Light Lesson 2 1 Questions from last class 1. What is Light? Light is the form of energy that we can see 2 Questions from last class 2. What are sources of Natural Light and why are they called “natural light”? They are called “natural light” because they are not made by humans Examples: the sun and other stars, Fire, Sparks, firefly, angler fish, northern lights, lightning 3 4 Questions from last class 3. How does the sun create light? Nuclear fusion: When hydrogen atoms fuse(combine) together under very large heat and gravity in the sun they create helium particles. During this process mass is lost and turned into energy(heat and light) because E=mc 2 5 Questions from last class 4. List at least 5 ways you’ve used light today? (include situations using reflection) Traffic lights Tv Computer lighting your room looking in a mirror cellphone Calculator food you ate digital clock 6 Sources of Light 7 Candle Observations: brightness, temperature, colour, etc how do you think the light is being produced? 8 Glow Sticks Observations: brightness, temperature, colour, etc how do you think the light is being produced? 9 Regular lightbulb Observations: brightness, temperature, colour, etc how do you think the light is being produced? 10 Spiral Bulb Observations: brightness, temperature, colour, etc how do you think the light is being produced? 11 glow-in-the-dark beads Observations: brightness, temperature, colour, etc how do you think the light is being produced? 12 Glowing Living things What do these all have in common? What does the light look most like? (think about the colour) 13 Incandescent Source An object that can be heated to such a high temperature that it emits visible light. 14 Luminescent Source An object that gives off light without heat Split into 4 groups.... 15 Fluorescent Source An electric current in a gas filled tube causes mercury vapour to produce ultraviolet light that then causes a phosphor coating on the inside of the bulb to glow. 16 Phosphorescent Source Light energy is absorbed by certain particles that can store this energy for a while. The stored energy is later released as visible light. 17 Chemiluminescent Source A chemical reaction between substances gives off light without creating heat. 18 Bioluminescent Source A form of chemiluminescence that occurs in living organisms. 19 Lightbulb Incandescent Source Electricity flows through the filaments creating a lot of heat and light Electrical energy → Thermal energy → Visible light energy 20 Electricity Moving electrons 21 Candle Incandescent Source Wick burns with fuel from wax (which is made of oil) 22 Glowsticks Luminescent Chemiluminescent A breakable barrier separates two liquids. Bending the stick causes the barrier to break. The liquids mix and cause a chemical reaction that releases glowing light. 23 Spiral Bulb Luminous Source Fluorescent Source CFL- Compact Fluorescent Source Electrical energy → Energy absorbed by mercury particles → Mercury gets excited → releases high energy UV rays → UV rays absorbed by phosphor coating → Visible light emitted by phosphor 24 Ultra Violet Light (UV) Light that has so much energy that humans can’t see it 25 Ultra Violet Light (UV) Why does white glow when you go glow bowling?!?! Particles in detergent absorb UV rays and emit visible light 26 Florescent Colours this? Why does this look brighter than Particles in Neon dye absorb UV rays and then emit light 27 Please recycle CFLs These bulbs are filled with mercury- a toxic chemical 28 Glow-Beads Luminous Phosphorescent Light is stored by particular particles in the beads then released even after the original light source is gone 29 Glowing Animals Luminous Bioluminescent Light is Created by living things due to a chemical reaction 30 Light Concept Map Read pages 207-209 Then create a concept map to show the relationships among the following terms: visible light, incandescent, luminescent, fluorescent, phosphorescent, chemiluminescent, bioluminescent, hot, not hot, candlelight, glow stick, spiral lightbulb(fluorescent bulb), normal lightbulb, glow-in-the-dark beads, and firefly visible light 31 Questions Read pages 207-209 1. What are UV rays and why can’t we see them? 2. Why do some white shirts glow under UV light and some don’t? 3. Explain how Regular Bulbs, Fluorescent bulbs, glow sticks and glow beads create light. 4. Why are Fluorescent bulbs more energy efficient than Incandescent bulbs? 5 .What is the main difference between fluorescence and phosphorescence. 32
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