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# Light waves

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Light Wave Notes

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• ### Light waves

1. 1. Ch 16Light Waves
2. 2. Light We see objects because light is either emitted or reflected by the object
3. 3. Light Light is an electromagnetic wave that the human eye can detect Light has wavelengths that range from 400 nm (violet) to 700 nm (red) The speed of light is 3 EE 8 m/s
4. 4. Luminous Body  Emits light waves  Ex: the sun
5. 5. Illuminated Body  Reflects light waves  Ex: the moon
6. 6. Luminous Flux (P) The rate at which light is emitted from a source It is measured in lumen (lm)
7. 7. Illuminance (E) The amount of light that is reflectedE= P 4 πd 2 Units are lm/m2 or lux (lx)
8. 8. Luminous Intensity (I) Luminous flux that falls on one square meter of a sphere one meter in radiusI= P 4π Units are candela (cd)
9. 9. Types of Materials
10. 10. Transparent  Transmits light without distortion  Ex: crystal clear water
11. 11. Translucent  Transmits light but the image is distorted  Ex: lampshade
12. 12. Opaque  Transmits no light  All light is absorbed or reflected  Ex: brick
13. 13. White Light Produced by adding the colors red, blue and green This is called the additive process Red, blue and green are called the primary light colors
14. 14. Mixing Light Colors Red and Green =  Yellow Blue and Green =  Cyan Red and Blue =  Magenta
15. 15. Complementary Light Colors Yellow and Blue  Produce white light Cyan and Red Magenta and Green
16. 16. Dyes and Pigments Dyes are molecules that dissolve in liquids to form colored solutions. They absorb certain wavelengths and reflect others. A pigment also absorbs certain wavelengths and reflects others, but they are larger and mix to form suspensions.
17. 17. Dyes and Pigments The absorption process of light forms colors by the subtractive process
18. 18. Primary Pigments Absorb one color from white light and reflect 2 colors Yellow absorbs Blue  Reflects red and Green Magenta absorbs  Reflects Blue and Red Green  Reflects Blue and Green Cyan absorbs Red
19. 19. Secondary Pigments Absorb 2 colors from white light and reflect one color Red absorbs Green  Reflects Red and Blue (Cyan) Green absorbs Red  Reflects Green and Blue (Magenta)  Reflects Blue Blue absorbs Red and Green (yellow)
20. 20. Complementary Pigments Produce black light Black is not a color just the absence of light No light is being reflected Note: The primary light colors are the secondary pigments and vice versa
21. 21. What color would a yellow bananaappear if it is hit with green light? Answer: Green, yellow can reflect red and green, but there is only green light hitting it.
22. 22. What color would a yellow banana appear if it is hit with blue light? Answer: Black, the yellow absorbs blue light so there is no light to reflect
23. 23. What color would a yellow banana appear if it is hit with cyan light? Answer: Green, the yellow absorbs blue light Cyan – Blue = Green
24. 24. Polarized Light  Light that only vibrates in one plane.  Polarized light will only pass through a polarized filter if it is parallel to the vibrating light
25. 25. Thin Film Interference The beautiful colors are caused when light reflects off of 2 surfaces Example: Oil and water or the 2 layers of a bubble