Light

1. Light Chapter 13

2. Ch13 Sec 1The Behavior of Light

3. Light and Matter • Objects must reflect light to be seen. • Opaque materials do not allow light to pass through them; they only absorb and reflect light

4. Light and Matter • Objects must reflect light to be seen. • Opaque materials do not allow light to pass through them; they only absorb and reflect light • Some light passes through translucent materials.

5. Light and Matter • Objects must reflect light to be seen. • Opaque materials do not allow light to pass through them; they only absorb and reflect light • Some light passes through translucent materials. • Transparent materials allow almost all light to pass through them; only a little light is absorbed and reflected.

6. Reflection of light • Reflection of light – a light wave strikes an object and bounces off. • Law of Reflection – angle at which light strikes a surface is the same as the angle at which it is reflected

7. Regular Reflection • Regular reflection – reflection of light waves from a smooth surface

8. Diffuse Reflection • Diffuse reflection – reflection of light waves from a rough surface

10. Refraction of Light • Refraction of light - change in the speed of a light wave when it passes from one material to another

11. Index of refraction • The index of refraction indicates how much a material reduces the speed of light; the more light is slowed, the greater the index of refraction.

12. Prisms • Separate white light into visible spectrum based on light wavelength

13. Rainbows • Caused by water droplets refracting wavelengths of sunlight

14. Chapter 13 Section 2Light and Color

15. Colors… • Colors are determined by wavelength of light an object reflects. • White objects reflect all colors of visible light. • Black objects absorb all colors of visible light.

16. Colors… • Colors are determined by wavelength of light an object reflects. • White objects reflect all colors of visible light. • Black objects absorb all colors of visible light. • Filter – is a transparent material that absorbs all colors except the color or colors it transmits • Filters can make objects appear to be different colors.

17. Seeing Color • Light enters the eye and is focused on the retina. • Retina – made up of two types of cells that absorb light

18. Seeing Color… • Light enters the eye and is focused on the retina. • Retina – made up of two types of cells that absorb light • Cones – distinguish colors and detailed shapes; most effective in daytime vision • Rods – sensitive to dim light; most effective in nighttime vision

19. Colorblindness Tests Normal color: yellow square & faint brown circle Colorblind sees: yellow square Test Name: Ishihara Test Colorblind sees: the number 17 Normal Color sees: the number 15

20. Colorblindness • Results from when one or more sets of cones do not function properly

21. Mixing colors • Pigment – colored material that absorbs some colors and reflects others

22. Mixing colors • Pigment – colored material that absorbs some colors and reflects others • Primary colors of light – Red, Green, and Blue • Primary colors of pigment – magenta, cyan, and yellow

23. Mixing colors • Pigment – colored material that absorbs some colors and reflects others • Primary colors of light – Red, Green, and Blue • Primary colors of pigment – magenta, cyan, and yellow • Primary colors of light are additive colors – combine to form white • Primary colors of pigments are subtractive colors – combine to form black, the absence of reflected light

24. Producing Light Chapter 13 Section 3

25. Incandescent lights • Hot tungsten wire glows; gives off light and heat

26. Fluorescent lights • Electrons collide with gas atoms, releasing ultraviolet radiation absorbed by phosphorus lining the bulb; gives off light Why are these better than Incandescent bulbs? • Less energy used • longer lasting

27. Neon lights • Tubes filled with gas (usually neon) produce light from electron collisions; different colors can be made by adding different gases

28. Sodium-vapor lights • Heated neon gas glows and warmth turns sodium into a vapor, producing a yellow-orange glow; used for outdoor lighting.

29. Tungsten-halogen lights • Have a filament and gas enclosed in a glass bulb to produce intensely bright light

30. Lasers • Light beam produced when identical atoms send off identical light waves; can be made from gases, liquids, or solids • FYI – LASER – Light Amplification by Stimulating Emissions of Radiation

31. Lasers • Light beam produced when identical atoms send off identical light waves; can be made from gases, liquids, or solids • Lasers produce coherent light – waves of some wavelength are aligned, and travel same direction • Incoherent light – waves of multiple wavelengths are not aligned, travel in many directions

32. Using Light Chapter 13 Section 4

33. Holography • Process used to create a three-dimensional photographic image of an object • Illuminating objects with laser light produces holograms. • Holographic images are difficult to copy.

34. Optical Fibers • Use a process called Total Internal Reflection in order to transfer information coded in light beams. • Total internal reflection – light strikes a surface between two materials and is completely reflected back to the first material.

35. Total internal reflection