How do these work?

1. How do these work?

3. How can peacock feathers create bright colors? Why do oil puddles or soap bubbles have colors?

5. When light (or sound) enters a new medium, the wave can be: 1/___________________ back into the original medium; 2/ __________________ at the boundary; or, 3/____________________into the new medium reflected absorbed transmitted reflected ray incident ray medium 1 energy absorbed (boundary heats) boundary medium 2 transmitted ray Which wave (ray) has the most energy? Which has the greatest amplitude? incident incident

6. When light passes into a denser medium, it__________________. slows down c = 3.0 x 108 m/s a/ Invacuum: v = ___________________ molecules b/ Inwater: c c c c Light is________________, then _______________from each molecule. _____________ molecules, it travels at a speed______________. absorbed emitted Between v = c c/ In glass: c c c c c c c Higher density  _____________________ _____________________ more interactions slower speed

7. vglass < vair Ex. Light passing from air into glass : ________________ Characteristics of the incident ray: vi _______________________________ fi _______________________________ li _______________________________ Ai _______________________________ determined by medium color found from l = v/f energy in wave incident ray air (medium 1) boundary glass (medium 2)

8. Characteristics of the reflected ray: vr fr lr Ar = vi, b/c it is in the same medium = fi, b/c it’s the same color = li, b/c l = v/f < Ai, b/c not all energy is reflected incident ray reflected ray air (medium 1) boundary glass (medium 2)

9. Characteristics of the transmitted ray: v2 f2 l2 A2 < v1 (given) = fi, b/c it’s the same color < li, b/c l = v/f < A1 b/c not all energy is transmitted incident ray reflected ray air (medium 1) boundary glass (medium 2) transmitted ray exactly the same Notice: fr, fi, and f2 are ___________________________!!!

10. When you put your hand in water… Does it look like this… or this? Water

11. In the new medium, the speed _____________ and frequency_________________________ , so the wavelength must ________________________ . Different materials slow the __________________ by different amounts. How much it slows is summed up in a quantity called the ______________________________ n, of a material. It is defined as the ratio of the speed of light _______________________ to the speed of light __________________________: "n" is called the ___________________ index because "slowing down" can cause light to ______________ (bend). Notice that n _______________________ because it is the ______________________________________________________ . changes remains the same also change speed of light absolute index of refraction , in a vacuum, c, in the material, v n = c/v refractive refract has no units ratio of two speeds, and the units cancel.

12. Physics Reference Tables, page 5, top:

13. Page 2, bottom: Note: This table is really only true for yellow light, and only approximately true for other frequencies

14. Ex: Determine the speed of (yellow) light in water. Given: nwater = 1.33 c = 3.00 x 108 m/s Unknown: v = ? n = c / v 1.33 = (3.00 x 108 m/s) / v v = 2.26 x 108 m/s

15. v1 l1 n2 l2 v2 n1 Ex: what is the relationship between v and n? v n = c / v n higher n  __________________  __________________ slower speed shorter wavelength To compare the speeds and wavelengths of two materials, use the equation: = =

16. Physics Reference Tables, page 5, top:

17. n2 v1 l1 = = n1 v2 l2 Ex: The wavelength of a certain laser in air is 780. nm. A CD is coated with a plastic material that has an absolute index of refraction of 1.55. Find the wavelength of the light in the CD laser n1 air CD n2 Given: l1 = 780. nm n1 = 1.00 780. nm 1.55 n2 = 1.55 = l2 1.00 Unknown: l2 = 780. nm/1.55 l2 = ? l2 = 503 nm

18. l1 l2 Ex: Laser light entering a CD:  shorter  can read more data