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Just in time Professional Development. Science Objects: ~10 hrs of online instructional interactive content. Light and Color Science Object. Introduction. Navigation. Introduction √. Introduction

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Science Objects: ~10 hrs of online instructional interactive content

Light and Color Science Object

Introduction

Navigation

Introduction √

Introduction

Throughout this Light & Color series you will explore light as electromagnetic radiation and the process of human light perception, with brief excursions into historical studies of light and color and the sometimes confounding nature of such an obvious and universally perceived phenomenon among sighted people. In each of the scenarios, activities and "thought experiments" presented you will be asked to make predictions and track your thinking against the experts. You will encounter various simulations that will help you explore color mixing in both transmitted and reflected light.

Navigation

Please select the “Navigation” tab at the top of this window to learn how to navigate through this science module.


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Instructional Content & Learning Goals: AAAS & NSTA Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Light and Color Science Object

Science Module Goal

Benchmarks

Key Idea

Evidence of Understanding

Standards √

Goal: Light & Color Science Module

The Learner will develop a scientific understanding of light, recognizing that color is an aspect of light (a small range of energy within the spectrum of radiant solar energy). Through interrogating the “light and color simulator” learners will explore prior conceptions about light perception and learn that the “color” of an observed object depends on the “color” of the source energy (white light spectrum or a portion thereof) as well as whether the object is “transmitting” the light/color or “reflecting” it. Primary “colors” of transmitted light, those detectable by the human eye, are Red, Green and Blue, and all other colors can be achieved through combinations of these. Mixing “transmitted light colors” is color addition.


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Benchmarks Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Light and Color Science Object

Science Module Goal

Benchmarks

Key Idea

Evidence of Understanding

Standards √

Benchmarks: Light and Color Science Module

This section lists all standards that are related to the topic of light. The Key Ideas that will be used as the learning goals for the Science Module and Learning Object are derived from these standards. While not all of the ideas in a particular standard may become part of this Science Module or Learning Object, the list provided here offers a wider view of the topic at hand.

Grades 9-12:

Below are the identified benchmarks for grades 9-12 that are addressed in part by the learning object "transmitted light: color addition".

* "Accelerating electric charges produce electromagnetic waves around them. A great variety of radiations are electromagnetic waves: radio waves, microwaves, radiant heat, visible light, ultraviolet radiation, x-rays, and gamma rays. These wavelengths vary from radio waves, the longest, to gamma rays, the shortest. In empty space, all electromagnetic waves move at the same speed-the speed of light".

* "Waves can superpose on one another, bend around corners, reflect off surfaces, be absorbed by materials they enter, and change direction when entering a new material. All of these effects vary with wavelength".

Grades 6-8:

Below are the identified benchmarks for grades 6-8 that are addressed in part by the learning object "transmitted light: color addition".

* "Light from the sun is made up of a mixture of many different colors of light, even though to the eye the light looks almost white. Other things that give off or reflect light have a different mix of colors".

* "Something can be "seen" when light waves emitted or reflected by it enter the eye - just as something can be "heard" when sound waves from it enter the ear. Light acts like a wave in many ways. Waves can help explain how light behaves. Human eyes respond to only a narrow range of wavelengths of electromagnetic waves - visible light. Differences of wavelength within that range are perceived as differences of color".


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Key Idea: Color Addition Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Light and Color Science Object

Science Module Goal

Benchmarks

Key Idea

Evidence of Understanding

Standards √

Key Idea: Color Addition Learning Object

The key ideas are derived from studying the different standards on a topic. While the Key Ideas may atomize or clarify a standard, or even leave certain ideas out, they should reflect the content in the standards as closely as possible. The Key Ideas should provide a clear and specific description of the ideas that the learner should understand after they have gone through a Learning Object.

Benchmarks and National Standards contain many ideas about light as a part of science literacy, including an understanding of the electromagnetic spectrum, wavelength, and the behavior of waves. One part of this complex understanding is visible light and the idea that white light is made up from a mixture of other colors. This Learning Object focuses on that idea. The Key Idea that follows incorporates understandings derived from state standards documents, and thus includes some things that do not appear in Benchmarks or National Standards.

For More Information

KEY IDEA

"White is not a color but rather the presence of all colors of visible light. The mixing of three distinct colors (primary colors) with varying degrees of intensity can produce a wide range of colors, including white light. The most common set of primary colors is red, green, and blue".


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Evidence of Understanding Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Light and Color Science Object

Science Module Goal

Benchmarks

Key Idea

Evidence of Understanding

Standards √

Evidence of Understanding: Color Addition Learning Object

Evidences of understanding describe what learners should be able to know and do to demonstrate their understanding of the Key Idea listed above. How will you assess them for understanding? How will you measure the learners? level of understanding through performance tasks? These performance tasks become the evidence of understandings?how you gauge the learners? understanding of the content.

For More Information

EVIDENCE OF UNDERSTANDING

Since the principles of color addition have important applications to color television, color computer monitors and on-stage lighting at theaters, assessment items should have the learner use the principles learned to use the simulator to produce a desired appearance.


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Throughout this Light & Color series you will explore light as electromagnetic radiation and the process of human light perception, with brief excursions into historical studies of light and color and the sometimes-confounding nature of such an obvious and universally perceived phenomenon among sighted people. In each of the scenarios, activities and "thought experiments" presented you will be asked to make predictions and track your thinking against the experts. You will encounter various simulations that will help you explore color mixing in both transmitted and reflected light.

Engage √

Explore √

Explain √

Elaborate √

Evaluate √

Scenario

Tristan and Sophie are best friends. One day while walking home after school, the two stop to rest at the lakeshore. Sophie says, "Wow, those birch leaves are the yellowiest yellow I've ever seen. They seem as pure yellow as the sky is blue." Tristan responds, "You know, if you put that yellow and the sky blue together you get green; as green as the grass we're sitting on!" Sophie, then says, "Actually, yellow and blue together make white, like the clouds."

If you were a part of this conversation with Tristan and Sophie, what would you say?

Who is correct, Tristan or Sophie? Why do you answer the way you do? In other words how do you know who is correct? Can both Tristan and Sophie be correct?

Why do you answer the way you do?


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Scenario

Simulation

Mixing Colors

Going Further

Engage √

Introduction

The human eye-brain system is wonderful and quite unique. Your brain and the light sensors in your eyes create your perception of color. With all that your eyes do for you, how well do you understand what you see?

Suppose we had a special color-detection meter. If we point it at any colored screen it tells us the color. Now suppose the two patches are made to overlap. The meter records that the overlap area is composed of two colors-red and green. But the fascinating thing is that our brain/eye system is telling us something else! Do you know what color you will see?

Explore √

Explain √

Elaborate √

Evaluate √

In this section you will develop an understanding of how three primary colors can be combined to create any color you can imagine. With this understanding, you will be able to predict the results of combining (adding) two or more colors together.


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Scenario

Simulation

Mixing Colors

Going Further

Engage √

Scenario

Tristan and Sophie have been approached by their school theater department and asked to assist with a stage play. The stage director wants them to help with lighting a scene in which a solo actor is on stage delivering a monologue about the four seasons: spring, summer, autumn, and winter.

The storyboard calls for the actor to be dressed in a full-length white robe. As she is delivering her lines, she will need to be illuminated with stage lighting that reflects the changing colors of the seasons.

Explore √

Explain √

Elaborate √

Evaluate √

There are three lights available for illuminating the stage and actor. Tristan and Sophie's task is to come up with the correct lighting scenario for the brief monologue by turning on one, two, or all three lights, and then by changing the color of each light at the appropriate time to simulate the changing seasons.

In order to accomplish their task, the two technicians-to-be have some work to do in getting completely comfortable with their understanding of color addition. Before they undertake this task, Tristan and Sophie will first need to learn how to operate the stage lights so that they can illuminate the stage with the desired colors. In anticipation of this unique problem-solving venture, Tristan and Sophie work together to collect their best ideas and understandings of light, color, and color addition.


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Scenario

Simulation

Mixing Colors

Going Further

Engage √

Simulation

So that you may aid Tristan and Sophie in their work, we have provided you with an application that simulates a theater stage. The simulation will allow you to combine different colored lights on the stage and observe the results. When you enter the theater, you will see the stage with the actor in the center. This actor is very accommodating because she will stand there for as long as you need her to. The three lights available to you are hanging from the rafters. Each light is directed at the actor on the stage. You may turn each light on or off, and change its color to red, blue, or green. To combine colors, you can project more than one light at the actor. Try different combinations and observe the results. Do the results match what you would expect to happen? Why or why not?

Explore √

Explain √

Elaborate √

Evaluate √

Think back to the earlier question about combining red and green. When you enter the theater, you might want to start by directing a red and a green light at the actor on the stage to see what happens. When you do this, the colored lights are both directed at a common object: the actor's robe. Therefore, their combined frequencies are now illuminating the object's surface, which is colored white (and therefore will reflect all light that falls on it). Predicting the observed outcome requires knowledge of how red and green light will interact on the object's surface. What color do you think will result from this combination?

Time to Practice!

It's now time for you to explore the stage lighting simulation for yourself. Click the button to enter the theater.

Theater Stage


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Scenario

Simulation

Mixing Colors

Going Further

Engage √

Mixing Colors

In thinking about the scenario of Tristan and Sophie as stage lighting technicians (and your role in anticipating their decisions), we will now explore, in more depth, the concepts of visible light perception, and the work of the human eye in detecting and transmitting color information to the thinking-interpreting brain.

Simple Color Addition: What the Eye "Sees"

In the following discussion we will explore color mixing, make predictions, and test them using a color-mixing simulator.

What happens when we combine colors? Once again, think back to the earlier question about combining red and green.

Explore √

Explain √

Elaborate √

Evaluate √

Q What color will result if those two colors are made to overlap?

O Magenta

O Yellow

O Blue

O Brown

Tries Remaining: 4

Compare this to the color you originally thought would appear. You should have a better idea now that you have explored the stage lighting simulation. If you observed something other than what you predicted you may wish to revisit your earlier ideas. Accommodating new information and experiences sometimes means having to rethink and modify prior theories.


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Scenario

Simulation

Mixing Colors

Going Further

Engage √

Mixing More Colors

Explore √

Compare this to the color you originally thought would appear. You should have a better idea now that you have explored the stage lighting simulation. If you observed something other than what you predicted you may wish to revisit your earlier ideas. Accommodating new information and experiences sometimes means having to rethink and modify prior theories.

Now let's explore other color combinations.

Q What color will result if you overlap the red and blue lights?

O Orange

O Green

O Cyan

O Magenta

Tries Remaining: 4

And now for one more...

Q What color will result if you overlap the green and blue lights?

O Red

O Cyan

O Orange

O Violet

Tries Remaining: 4

You should remember these combinations from interacting with the stage simulation. However, if you need to return to the simulation to make sure, click on the following button:

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Scenario

Simulation

Mixing Colors

Going Further

Engage √

Going Further

Now let's take it a step further. Suppose you observed two other patches of colored light: blue and yellow. If the two patches are made to overlap, what color would you see, and why do you think so?

You may need to return to the stage simulation to figure this one out:

Explore √

Explain √

Elaborate √

Evaluate √

Theater Stage

What color is actually observed in the region of overlap when blue and yellow mix? Is this different from what you predicted? If this result did not agree with your prediction, then the good news is that there is something to learn.


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Color Spectrum

Secondary Colors

White Light

Practice

Review

Engage √

Explore √

Introduction

As you gather your thoughts and predictions, and findings, remember the importance of writing them down. This will help you organize your evolving ideas and allow you to go back and check predictions, discover patterns, confirm or question earlier thoughts and in general track your progress. The following discussion, along with its images, sketches, and diagrams, may help you build a more complete understanding of light and color and color mixing. First, we will start with a brief description of the color spectrum and primary colors.

Color Mixing Simulator

We have created a Color Mixing Simulator to allow you to explore color the various combinations of primary and secondary colors in the absence of the lighting scenario. This simulator allows you to select three different colors and then overlap them in various ways. Click the button below to load the simulator.

Color Mixing Simulator

Explain √

Elaborate √

Evaluate √


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Scott M. Graves Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Color Spectrum

Secondary Colors

White Light

Practice

Review

Engage √

The Color Spectrum

The full spectrum of visible colors ranges from violet-indigo-blue-green-yellow-orange-red.

Full solar spectrum (visible light)

We can simplify the continuous spectrum of rainbow colors by identifying a small set of basic colors in the visible spectrum. This includes blue, cyan, green, yellow, orange, and red.

Although you probably recognize more colors than this in your own observations of nature (consider all the colors in a rainbows or a prism dispersed colors set), the list here includes just a select few (6). And yet, these six colors are still more than the minimum-necessary to consider when exploring what our eyes respond to in the visible spectrum. This list of six colors is typical of what you might find in a simple set of crayons or paints (plus white and black). Interestingly, this same list of six colors includes an even smaller set of "primary colors" - the only colors in visible white light that your eyes have specific detectors for (for more on the human eye and its visual receptors, see the Elaboration section). So which are the "primary colors"? And how is it that we can "see" other colors - for example, brown, purple, pink, and magenta.

Explore √

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Color Spectrum

Secondary Colors

White Light

Practice

Review

Engage √

Color Perception: Primary Colors

The primary colors are red, green, and blue:

From these colors we can obtain any other color in the spectrum.

Recall your experiences with the stage lighting simulation. When you overlapped the green and red lights you produced a new color: yellow. Similarly, when blue and green were overlapped, they produced the color cyan (a bluish green color). Finally, when blue and red were overlapped they produced the color magenta (a pinkish-purple color). These results can be seen when the three primary colors are overlapped, as in the image below:

Primary Colors Overlapping

Notice that where the circles overlap, there is a new color. Some of this may seem obvious, and some of it may not. Blue and green creating cyan seems obvious, but many of us are surprised to find that green and red produce yellow. We might have predicted that mix to produce brown. That prediction likely stems from our previous experiences mixing pigments. Pigments are materials that reflect some but not all light, and mixing them results in the further reduction of light reflected, so the colors get progressively darker the more pigments we mix. In actuality, the mixing of pure red and pure green pigments should result in the total absorption of all light so that the mixture appears black. So what is happening when colored lights are mixed?

Explore √

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Color Spectrum

Secondary Colors

White Light

Practice

Review

Engage √

Secondary Colors

The colors that result from the mixing of the primary colors are called the Secondary Colors. This includes yellow, cyan, and magenta. Consider the following graphics:

In the first one, the primary colors red, green, and blue appear. Their overlapping regions produce additional colors. These are the secondary colors of cyan, yellow, and magenta. To help visualize the mixing "rules" for primary light, it might help to consider a process of mixing only two primary colors at a time. Refer to the graphic at right to see the mixing products between any two of the primary colors.

Give it a Try!

You can achieve the same effect using the Color Mixing Simulator. Simple make each square one of the primary colors, and then move them so that they overlap. Try it!

Color Mixing Simulator

Explore √

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Color Spectrum

Secondary Colors

White Light

Practice

Review

Engage √

Secondary Colors (cont.)

To really appreciate the mixing "rules" for colored light it helps to refer back to the full visual spectrum of solar colors.

Notice that there are intermediate colors between the primary and secondary colors. These are produced by varying mixtures, with subtle gradations in hue (color) created by precise add-mixtures along the spectrum. In general, adding adjacent colors produces intermediates. Some other common colors we see every day are produced by more complex mixtures of specific colored light sources. For example, "sky blue" is a lighter hue than pure blue light, but not as "greenish" as cyan. Similarly, "sea green" is an intermediate between cyan and green. "Grass green" is a mixture of green and yellow. Orange is a mixture of red and yellow light.

From this understanding of the Spectrum and color mixing among adjacent pairs of primary of secondary colors, you might predict some additional possibilities. For example, what is the result of mixing cyan and orange? Blue and yellow?

Finally, from looking at the spectrum above, what would you expect the result to be from mixing red and blue? Think about it for a minute, and then move your mouse over the button:

Explore √

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Color Spectrum

Secondary Colors

White Light

Practice

Review

Engage √

White Light

Notice that in the graphic you saw earlier, the central part

where all three primary colors meet is colored white:

The color white is obtained by adding all of the colors in the visible spectrum together. Since all of the spectral colors can be obtained through various combinations of red, green, and blue (the primary colors), mixing all three of them together will give us white. Earlier, you probably noticed in the stage lighting simulation that if you turned on a red light, a green light, and a blue light, the actor was illuminated in white light.

Two-Color Combinations

In addition, there are at least three combinations of two colors (referred to as "complementary colors") that produce white when added together. See if you can figure out which combinations of primary and secondary colors will produce white by using the Color Mixing Simulator. Click the button below to load the simulator. Start by mixing the colors blue and yellow, and then try other combinations.

Color Mixing Simulator

Once you've finished with the simulator, answer the following question:

Using only the primary (red, green, and blue) and secondary colors (yellow, cyan, and magenta), how many combinations of two colors produce white light?

O 2

O 3

O 5

O 6

Tries Remaining: 10

Explore √

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Color Spectrum

Secondary Colors

White Light

Practice

Review

Engage √

Two-Color Combinations (cont.)

If you remember from earlier, combining all three of the primary colors will produce white light. Since red and green combine to produce yellow, adding blue to yellow is the same as adding all of the three primary colors to begin with.

Here's a rundown:

Red + Green + Blue = White

Red + Green = Yellow

Therefore,

Yellow + Blue = White

The following diagram shows all of the two color combinations that produce white. Notice that in each case, a secondary color is combined with a single primary color.

Two-color combinations that produce white light.

Explore √

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Color Spectrum

Secondary Colors

White Light

Practice

Review

Engage √

Practice

Let's see what you've learned so far. Take another look at the color mixing questions you saw earlier in this learning object:

Q What color will result if you overlap the red and green lights seen above?

O Magenta

O Yellow

O Blue

O Brown

Tries Remaining: 4

Q What color will result if you overlap the red and blue lights seen above?

O Orange

O Green

O Cyan

O Magenta

Tries Remaining: 4

Q Finally, what color will result if you overlap the green and blue lights seen above?

O Red

O Cyan

O Orange

O Violet

Tries Remaining: 4

Explore √

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Introduction

Color Spectrum

Secondary Colors

White Light

Practice

Review

Engage √

Review

Let's see what you've learned so far. Take another look at the color mixing questions you saw earlier in this learning object:

The Primary Colors and their Secondary Mixing Results.

Explore √

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Light Energies

Seeing Visible Light

Computer Screens

Engage √

Explore √

Introduction

The following narrative, along with the accompanying images, sketches, and diagrams may help you solidify your understanding of light and color and how humans perceive color mixing. As you progress through the rest of this science object?s activities, you may well be satisfied that you know how colors combine together to produce other colors, and how the brain works to allow you to see colors that are not actually there.

Light as Radiant Energy

Explain √

Elaborate √

Evaluate √

What we refer to as light (and by extension, color) is energy in the form of electromagnetic radiation, whose origin is our sun. The sun radiates energy across a very broad "spectrum" or continuum of energies. A classic explanation of light energy was drafted as early as the late 1600's by Christiaan Huygens, who described a simple model of light rays and waves propagating through the ether. Discrete aspects of this overall solar spectrum of energies are known by their "frequencies" or "wavelengths". These wavelengths are measured in meters and nanometers (one millionth of a meter).


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Light Energies

Seeing Visible Light

Computer Screens

Engage √

Light as Radiant Energy (cont.)

The illustration below shows the entire electromagnetic spectrum:

This illustration also identifies the visible spectrum as a narrow range of frequencies and energies within the overall spectrum. The eye cannot sense radiation with wavelengths shorter than 400 nanometers or longer than 700 nanometers. The portion of the sun's radiant energy that is perceptible by the human eye is what we call visible light. This narrow range of (visible light) energy frequencies is centrally located in the electromagnetic spectrum (refer to figures above and below). As we move through the visible spectrum of violet, blue, green, yellow, orange, and red, the wavelengths become longer.

Explore √

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Light Energies

Seeing Visible Light

Computer Screens

Engage √

Close-Up of Visible Spectrum

As you can see from the illustrations, the full spectrum of solar radiation includes energies beyond the range of visible colors. Infrared and radio waves are at the long wavelength (low energy) side of the electromagnetic spectrum, while ultraviolet (UV), x-rays, and gamma rays lie at the short wavelength (high energy) side. Wavelengths of light shorter than 400nm and longer than 700nm (the bounds of the visible spectrum) are beyond the capacity of humans to detect without special tools. Your eye does not respond to these energies, but they can tell us a lot about a light source. The spectra outside (beyond) the red side of the spectrum of visible light contains "infrared colors" or "infrared radiation". Included in this region is the radiation your body gives off as well as the warmth that the earth gives off. This radiation is often called heat, but it is properly referred to as infrared radiation. Also included in this region, beyond the red and infrared, are microwaves and radio waves. On the other side of the spectrum, beyond the deepest blue violet, are ultraviolet, x-ray, and gamma rays.

Dangerous Energies

These frequencies of light outside the visible spectrum have high energy and can be dangerous. For example, our skin can detect ultraviolet light; there is, however, a time lag between sensing (often called exposure) and our recognition of UV light. This high-energy light often destroys cells and in general is harmful to people. It is the source of the "sunburn" phenomenon. Light from the sun is absorbed by the earth's atmosphere in the ultraviolet (UV) and infrared (IR) regions, but some of it reaches the earth. The UV portion that causes sunburn can be blocked by glass, and much of the light is blocked by water except for the blue (B) and violet portions. It is the presence of water in our atmosphere that scatters much of the blue light, and thus the skies often appear Blue.

Even though we cannot see them, scientists have created detectors that work well in the infrared, visible, and ultraviolet regions; indeed, the entire spectra is what scientists have to work with when they sense radiation from far distant objects in the sky, such as stars, galaxies, and quasars.

Back here on earth, other creatures' eyes often have light receptors that respond to frequencies we humans cannot see. So some animals and insects can "see" in the ultraviolet and infrared.

Explore √

Explain √

Elaborate √

Evaluate √


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Light and Color Science Object Standards-based content, focused topical treatments, multiple styles of interactivity (Java & Flash simulations, animations), interactive feedback in Assessments/Evaluations.

Light Energies

Seeing Visible Light

Computer Screens

Engage √

Seeing Visible Light

For most people, sight is the most heavily relied upon of all the senses. Information gathered by our eyes accounts for up to 90 percent of what we rely upon day-to-day, minute-to-minute. And yet, most of the biological and neurological processes of sight perception, let alone the physics of light, we take for granted.

Early in our schooling, most of us learn primary colors as pigments and spend many hours experimenting with mixtures of paint, chalk, and crayon. However, the understanding of color we come away with is often incomplete and may lead to misconceptions.

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The process of seeing began very early in biological evolution. In the ancient seas, life forms developed light-sensitive tissues. Our human connection to those earliest of photoreceptors, and a reminder of our oceanic origins is recognized in the necessary and constant bathing of our eyes in a thin layer of salty tears.

Primitive Sight

Very simple creatures with primitive eyes, flatworms are multicellular organisms. They possess simple eyes and a simple nervous system. (Image from the Institute for the Promotion of the Less than One Millimeter: Micropolitan Museum: Freshwater Collection.)


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Light Energies

Seeing Visible Light

Computer Screens

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Light Reception

We can describe light as electromagnetic waves, with color identified by its wavelength. We can also consider light as a stream of minute packets of energy-photons which create a pulsating electromagnetic disturbance. A single photon of one color differs from a photon of another color only by its energy. Our perception of color arises in physical-chemical-neurological interactions in the eye and brain. These interactions, initiated by the presence of light and the specific neurological responses, are driven by the composition of the incoming light - the energy spectrum of photons - that enter the eye. The diagram below shows a cross-section of the human eye. To the right is an expanded view of a small section of the retina, with its photoreceptor cells identified. Note the difference in the number of neural connections (ganglion) for rods and cones.

Cross-sectional representation of the eye showing light entering through the pupil. The photosensitive cells, cones & rods, are located in the retina: cones respond to color, rods to light intensity.

The retina on the inner surface of the back of the eye contains photosensitive cells. These cells contain pigments that absorb visible light. Of the two types of photosensitive cells, rods and cones, it is the cones that allow us to distinguish colors - light/photon energies or frequencies. The rods are effective in dim light and react to changes in light intensity - the flux of incident photons - not photon energy. The cones do not operate below a certain light threshold, so in dim light, with primarily the rods at work, we perceive colored objects as shades of grey, not shades of color.

Why Both?

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Light Energies

Seeing Visible Light

Computer Screens

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We need two types of photoreceptors because we live in a world of darkness and light (night and day). The rods and cones function to gather light of quantitatively and qualitatively different aspects. Color is perceived in the retina by three sets of cones (photoreceptors) with sensitivity to energies broadly overlapping the blue, green, and red portions of the spectrum. For every color signal or flux of photons reaching the eye, some ratio of response within the three types of cones is triggered. It is this ratio that the eye-brain system interprets as the perception of a particular color.

A hundred and twenty five million thin, straight rods cells in the retina gather light in the shadows, at dusk and dawn, and in the faintest moon or starlight. The rods do not sense individual "colors", but can detect a single photon. The rods "see" in black and white, and that is why our vision at night seems mute of hue and color. Seven million cones (thicker than the rods) in the retina are selectively sensitive to one of 3 basic color "frequencies": red, green, or blue. With just these three colors, our eye-brain makes full spectacular and Technicolor visions of the world.

The Fovea

The "fovea" region of our eye is a small patch of densely packed cones in the primary focal point of the retina (in the diagram above it appears as a small divot at the back of the retina facing directly across to the lens and pupil). There, most every cone has a direct connection to the visual cortex, so subtleties up close, in bright light, and in the primary focus region of our gaze are very well resolved. However, the fovea is a very small region of the retina; elsewhere the rods and cones are less dense, so our eyes are constantly moving to keep the light from objects of interest cast upon the foveal receptors.

In dimly lit situations, say when you are starring deep into a dark part of the night sky, the foveal cones are almost useless, so we often have to "look" off to the side of our intended visual target to allow nearby rods to gather and resolve their light.

So, with receptors for red, green, and blue, the human eye/brain perception system can effectively ?see? the full spectrum of colors.

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Light Energies

Seeing Visible Light

Computer Screens

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Computer Screens

Next turn your attention to a computer screen or television monitor. Recalling that adding individual colors to a dark screen creates color mixtures, the question asked now is, "how does this color addition really work?"

Consider the two images below. The second is the same as the first, stretched to double the original size. Look carefully at the yellow, cyan, and magenta regions.

In the upper (smaller) diagram your eye may have difficulty resolving the individual colors within the yellow, cyan, and magenta regions. They are just small enough that your brain and eye instead work to interpret the cluster of different hues and adds them together to arrive at a single color (e.g., cyan = blue + green).

With a magnifying glass, you can similarly look at any computer monitor and see that colors other than red, green, and blue are actually made up of combinations of red, green, and blue "pixels" at various intensities.

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Light Energies

Seeing Visible Light

Computer Screens

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Combining Phosphors

Computer screens, like televisions, control red, blue, and green "phosphors" (elements shown at right), and our eye then adds these colors where they are adjacent to produce a blended mix. Where larger areas of the screen are all illuminated by a single color (phosphor), that area will appear to be a single color.

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However, the individual phosphors are very small and where adjacent phosphors glow with different intensities, your human brain tries to resolve them by "blending" the signal the eye receives. TV monitors are sometimes called R-G-B monitors. Digital cameras are also designed to model the 3 color receptors in our eyes. There are 3 detectors designed to see (detect) red, green, and blue colors.


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Light Energies

Seeing Visible Light

Computer Screens

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Another example of this phenomenon appears in the following penguin images. The image on the left shows the normal screen image, while the image below shows the same image of a computer screen magnified.

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The enlarged image shows the three distinct phosphors (red, green, and blue) used to achieve the full-color image of the toy penguin. Notice how the image is created by the changing brightness of adjacent colored phosphors.

The yellow-looking areas (the penguin's beak and feet) are achieved with mixtures of only two phosphors: green and red. Notice also that areas appearing dark (black) occur where the phosphors are all at lowest luminosity (turned off). Similarly, white areas are created by an equally bright mix of all three phosphors.


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Introduction

Stage Lighting

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Stage Lighting Revisited

Let's think back to the first part of this science object

and the scenario involving Tristan and Sophie, and see I

f we can help them achieve their goals.

Review of Scenario

Tristan and Sophie have been approached by their school theater department and asked to assist with a stage play. The stage director wants them to help with lighting a scene in which a solo actor is on stage delivering a monologue about the four

seasons: spring, summer, autumn, and winter.

The storyboard calls for the actor to be dressed

in a full-length white robe. As he is delivering

his lines, he will need to be illuminated with

stage lighting that reflects the changing colors

of the seasons. There are three lights available

for illuminating the stage and actor. Tristan and

Sophie?s task is to come up with the correct l

ighting scenario for the brief monologue by

turning on one, two, or all three lights, and then

by changing the color of each light at the

appropriate time to simulate the changing seasons.

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Introduction

Stage Lighting

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Your Task

Imagine a stage actor dressed in a white robe, strolling across the stage. Consider the changing colors of the actor's garment as he moves about on stage among the lights. There are only three lights available for illuminating the stage and actor. Each light can be turned on or off, and when turned on can be switched to either red, green, or blue. Your task is to come up with the correct "lighting scenario" to simulate the changing seasons, directing either one, two, or all three lights to be on or off, and determining which color combinations to use at the appropriate time for each season.

Remember that it is the overlapping (addition) of lights that creates colors other than those in the standard set. When two or more colored lights are directed at a common object, their combined frequencies illuminate the object's surface. Predicting the observed outcome requires knowledge of how each color combination will interact on the object. Also remember that you can leave a light "off" if necessary.

How confident are you that you can correctly light the stage play?

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Introduction

Stage Lighting

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Scene1

The curtain rises, and the actor enters the stage from the right and strolls to a position on the left side of the stage. She then addresses the audience:

Four Seasons fill the measure of the year;

There are four seasons in the mind of man:

At his point, she should be illuminated with white

light. Which lights do you need to turn on in order to

illuminate the actor with white light?

Drag the appropriate lights over to the "Stage Lights" area.

Tries Remaining: 2

Scene 2

The actor continues her monologue. The season is spring:

O Thou with dewy locks, who lookest down

Thro' the clear windows of the morning, turn

Thine angel eyes upon our western isle,

Which in full choir hails thy approach, O Spring!

For this season, the actor should be illuminated with green

light. Which lights do you need to turn on in order to illuminate

the actor with green light? Drag the appropriate lights over to the "Stage Lights" area.

Tries Remaining: 2

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check

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reset


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Introduction

Stage Lighting

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Scene 3

The actor moves slowly a few paces to nearly the middle of the stage.

The season changes to summer:

O thou who passest thro' our valleys in

Thy strength, curb thy fierce steeds, allay the heat

That flames from their large nostrils! thou, O Summer,

Oft pitched'st here thy golden tent, and oft

Beneath our oaks hast slept, while we beheld

With joy thy ruddy limbs and flourishing hair.

For this season, the actor should be illuminated with

yellow light. Which lights do you need to turn on in order to

illuminate the actor with yellow light?

Drag the appropriate lights over to the "Stage Lights" area.

Tries Remaining: 2

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Introduction

Stage Lighting

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Scene 4

The actor continues her monologue as she moves further right

across the stage. The season changes to autumn:

O Autumn, laden with fruit, and stainèd

With the blood of the grape, pass not, but sit

Beneath my shady roof; there thou may'st rest,

And tune thy jolly voice to my fresh pipe,

And all the daughters of the year shall dance!

Sing now the lusty song of fruits and flowers.

For this season, the actor should be illuminated with

orange light. Which lights do you need to turn on in

order to illuminate the actor with orange light?

Drag the appropriate lights over to the "Stage Lights" area.

Tries Remaining: 2

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Introduction

Stage Lighting

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Scene 5

The actor strolls to her final position furthest to the right on

stage. The season changes to winter:

O Winter! bar thine adamantine doors:

The north is thine; there hast thou built thy dark

Deep-founded habitation. Shake not thy roofs,

Nor bend thy pillars with thine iron car.

For this season, the actor should be illuminated

with cyan light. Which lights do you need to turn

on in order to illuminate the actor with cyan light?

Drag the appropriate lights over to the "Stage Lights" area.

Tries Remaining: 2

Conclusion

The actor concludes her monologue:

Autumn to winter, winter into spring,

Spring into summer, summer into fall,--

So rolls the changing year, and so we change;

Motion so swift, we know not that we move.

She then leaves the stage to the right.

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Introduction

Stage Lighting

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Below is an image displayed on a computer screen.

Which of the following answers best describes the

process that is happening when the monitor displays

the image?

O The monitor contains phosphors that can display various shades of black, white, and grey based on the information sent to it from the computer. The rods in your eyes interpret these various intensities of light, and construct a black and white image that matches the one displayed by the monitor. Then the cones in your eyes do their part by adding the color information to create a full color image.

O Information about the image is sent to the monitor by the computer. The monitor then projects all the necessary colors onto its screen. The phosphors inside the monitor can project all of the colors of the spectrum to create any image necessary. Your eyes then interpret these colors and intensities using the rods and cones inside the retina.

O Like photographic film, the monitor's screen is sensitive to various colors and intensities of light. When the screen is exposed to the light projected by the computer, the image is developed on the screen, much like a photograph is developed in a darkroom. The rods and cones in your eyes then interpret this computerized "photograph", and an image is sent to your brain.

O The monitor contains red, green, and blue phosphors. These phosphors are being turned on and off to make the appropriate colors appear on the screen. Various intensities of red, green, and blue can be combined to give the appearance of other colors.

Tries Remaining: 2

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Introduction

Stage Lighting

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The Electromagnetic Spectrum

Place the following light energies in the order they fall on the electromagnetic spectrum, from

high energy (short wavelength) to low energy (long wavelength). The following image will help

you get started:

__ Microwave Rays

__ Radio Waves

__ UHF-VHF-TV Waves

__ Visible Light

__ Gamma Rays

__ Ultraviolet Rays

__ Infrared Rays

__ X Rays

Tries Remaining: 3

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Introduction

Stage Lighting

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Light Reception

The image below shows an expanded

view of a small section of the retina.

Drag the labels from the right and place

them on top of the correct part of the eye.

Tries Remaining: 2

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Which photoreceptors in the human eye respond to the following stimuli? For each stimulus

listed at the bottom, check the box that corresponds to the appropriate photoreceptor.

1. Mostly Cones

2. Rods

3. Mostly Rods

4. Cones

Light Intensities 1 2 3 4

Light Frequencies 1 2 3 4

Moonlit Shadows 1 2 3 4

Daylight Colors 1 2 3 4

Tries Remaining: 2


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End simulation ….


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