Placemat activity different types of light
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Placemat Activity: Different Types of Light. Unit 4: Chapter 10 – Sources and Nature of Light (p.403-410). Artificial Genetically modified zebrafish emit visible light when exposed to UV radiation. Natural Algae and bacteria are able to emit light naturally Bioluminescence.

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Placemat Activity: Different Types of Light

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PlacematActivity: Different Types of Light


Unit 4: Chapter 10 – Sources and Nature of Light (p.403-410)

Artificial

  • Genetically modified zebrafish emit visible light when exposed to UV radiation.

    Natural

  • Algae and bacteria are able to emit light naturally

    • Bioluminescence


Bioluminescence


What is light?

  • Light is a form of energy known as electromagnetic waves

    • When energy is absorbed electrons move to an excited state.

    • These excited electrons release energy in the form of light.

  • In other words, the light that is seen is the light that is emitted, NOT ABSORBED

    • E.g. Chlorophyll is green because it does not absorb green light


Types of Light Emissions

  • There are three types of light emissions:

    • Light from the sun

    • Light from incandescent

    • Light from electric discharge


Sun light

  • Hydrogen atoms in the Sun’s core are moving at rapid speeds and colliding with one another

  • These collisions will sometimes cause two Hydrogen's to fuse together forming Helium.

    • A fusion reaction

  • This reaction releases a ton of energy creating light.


Sunlight

  • Sunlight emits white light which is made up of all light colours.


Incandescent Light

  • Incandescent light occurs when a metal is heated to produce light

    • Tungsten wire is typically used because of its brightness when heated

  • It is inefficient at producing light since only 5% of the heat used produces light.

    • The other 95% is lost as heat


Incandescent Demonstration Copper Penny

  • Why might an older penny (1962- 1982) be more effective at producing light when heated?


Electric Discharge Light

  • Electric discharge light is produced when an electric current passes through a gas source

    • The electrons within the gas become excited causing them to release light.

  • Various gases emit different light sources


  • Where might you see various gases being used to produce light?

    Christmas lights

    Signs

    Traffic lights

    Fireworks


    Fluorescent Light

    • Fluorescent lights are commonly found in school, businesses, and various other industries.

    • Fluorescent lights are composed of a phosphor powder coating, mercury, and a noble gas.

    • At each end of a fluorescent light there is an electrode.


    Fluorescent Light (Fig 10.5)

    • When an electric current is applied to a fluorescent light bulb, electrons collide with mercury atoms.

    • The mercury will then release UV radiation (not visible) which is absorbed by the phosphor coating

      • The phosphor coating emits visible fluorescent light


    Demonstration: Blacklight Applications

    • Ask students for cash money, tell them thank you, I have just demonstrated how easy it is to get people to give you money.


    Literacy Check: Fluorescent Applications

    • In the same group as the placemat, read page 406 (Figure 10.7)

    • Create a short scenario (4-5 sentences) where fluorescence may be used. Explain how fluorescence helped resolve the problem.


    Types of Luminescence

    • Luminescence:

      • Is the light produced without heating an object

      • Fluorescence is a type of luminescence because it does not use heat to produce light

      • Phosphorescence, chemiluminesence, and bioluminescence are all prime examples of luminescence.


    1. Phosphorescence

    • Phosphorescence:

      • Is similar to fluorescent light because it uses UV light to create light

      • However, the major difference is that phosphorescence glows long after the UV light has been absorbed


    2. Chemiluminescene

    • Chemiluminescence is light that is generated by the energy released in a chemical reaction.


    3. Bioluminescence

    • Bioluminescence is a form of chemiluminescence

      • Occurs where energy is released by a chemical reaction in the form of light.


    Homework

    • Answers questions #1-4 (p. 407)

    • Notes: Question number one discuss the “excited atom”. In this lesson we have focused on the “excited electron” which is part of the atom.


    The Nature of Light

    • Light is energy that travels like a wave through empty space.

      • Electromagnetic waves

    • Electromagnetic waves function as ocean waves as they have a crest and a trough


    Light as Waves

    • The wavelength of light is the distance between troughs or between crests.

    • Electromagnetic waves are made of both a magnetic and a electric field.


    The Electromagnetic Spectrum

    • Waves exist along a continuum of various wavelengths

    • The smaller the wavelength, the higher in energy the light

    • The longer the wavelength, the lower in energy is the light


    Homework Questions

    • Read pages 403-410

    • Answer questions #1-7 (page 410)


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