Light. Light. Light is a form of energy called radiant energy. The Sun gives off huge amounts of energy called electromagnetic radiation or radiant energy. This energy travels to Earth in a vacuum of space. . Some of this E-M or radiant energy you can see some you can’t
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Light is a form of energy called radiant energy
The Sun gives off huge amounts of energy called electromagnetic radiation or radiant energy.
This energy travels to Earth in a vacuum of space.
Light starts many chemical
reactions such as photosynthesis
can cause changes in matter The light energy is changed
to other forms of energy
Sunlight heats the
water in the ocean
Is this a change in the form of energy?
Remember chemical reactions?
Many give off light.
So, how does light travel?
Photons! Tiny invisible particles of energy!
Photons are energy, not matter, so no weight!
Wow, I am as light as a photon!
But, I still don’t get it!
How do the photons get to where they are going?
Light moves in waves!
No, not those waves!
Light Waves like this!
Geez! Do I always have to tell you guys everything?
A wave is energy that moves through a
medium (solid, liquid, or gas)
But however they travel…..
light waves all travel through space at the same speed and they can all travel through a vacuum.
Nothing is a fast as the speed of light….well almost nothing!
It travels 300,000 km/s!
Light could travel around the world 7.5 times in 1 second!
Waves – light waves that is
Crest – highest point of the wave
Trough – lowest part of the wave
Hmmm.. Does this sound familiar?
Who remembers waves from our ocean unit?
Light Waves are measured according to:
the number of waves that pass a point in a specific amount of time (like a second)
measurement from the crest of one wave to another crest
measurement from crest to the midline, or crest to trough
divided by two
High frequency wave= short wave length =
Low frequency waves =
longer wave length =
How Light Behaves
“Light”, the dog
Light behaves in different ways when it strikes different things
Light slows down - bends – or bounces back when it travels through different mediums like gas, liquids, or solids
We’ll learn in the next unit that sound is just the opposite!
Sound waves speed up when they travel through
different mediums such as gas, liquids, or solids.
What we see is white light
that is actually made up of many colors of light
We can only see
these colors when
reflected or refracted
ROYGBIV – the visible light spectrum
ROYGBIV The visible light spectrum
Red – Orange – Yellow – Green – Blue – Indigo - Violet
the return of light or sound as it bounces off a surface
Reflection is the way we see most things!
The colors of light that an object reflects are the colors we see.
For example: an apple absorbs most of the sunlight that strikes it.
The rest of the light – the red part – reflects off the apple.
That’s why the apple appears red to us.
slowing down of
A prism works like a rainbow!
It separates white light into the spectrum known as
ROY G BIV.
When light passes into the prism glass it slows down and bends. This is known as
Rainbows are produced when white light strikes drops of water.
Each drop acts like a prism that separates the white light into
No light passes through
Example – wood, foil, 50 sheets of paper
Allows all light rays to pass through
Example - glass, shallow water
Allows some light rays to pass through
Example: wax paper – one piece of paper
Each table will have one container of objects.
Experiment with the prism to find ROYGBIV
Experiment with the disk to find ROYGBIV
Answer questions on the ROYGBIV worksheet
Find your What’s Blocking the Light worksheets in packet
Choose an object such as a pencil or eraser.
Now take a material that you believe is transparent from
Your box of goodies.
Observe what happens when you place it over the object you
Draw in the cloud what you observe.
Write about what you observe
Do the same for translucent and opaque
When finished, try experimenting with other materials in box
Fill in boxes with materials that are transparent, translucent and opaque
the bending & slowing down of light waves when they pass from one kind of matter to another
A mirage is an example of light refraction.
The difference in air temperature bends the light
A lens that is wider at the edges than in the middle, and
That refracts light rays so they bend outward
A lens that is wider in the middle than it is at the edges
It refracts light rays so they come together.
Nearsighted means you can see
close up, but not far away.
Concave lenses correct nearsighted vision.
Farsighted means you can see faraway objects,
but not close up objects.
Convex lenses correct farsighted vision
Other examples of convex lenses are:
magnifying glasses, telescopes, microscopes, & binoculars
How do we see?
Our eyes are like cameras
The pupil is the opening
Iris – controls the amount of light that enters the eye
Retina – a layer of light sensitive cells at the back of the eye
The retina sends a signal to our brain to tell us what we are seeing
Hey can someone turn off the light?