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 medium 1 medium 2 boundary incident ray reflected ray transmitted ray energy absorbed (boundary heats) Which wave (ray) has the most energy? Which has the greatest amplitude? reflected absorbed transmitted incident

6. When light passes into a denser medium, it__________________. c = 3.0 x 10 8 m/s a/ In vacuum: b/ In water: c/ In glass: molecules c cc c Light is________________, then _______________from each molecule. _____________ molecules, it travels at a speed______________. c c c c c c c Higher density  _____________________  _____________________ slows down v = ___________________ absorbedemitted Between v = c more interactions slower speed

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

8. v r f r r A r = v i, b/c it is in the same medium = f i, b/c it’s the same color = i, b/c = v/f air (medium 1) glass (medium 2) boundary incident ray reflected ray < A i, b/c not all energy is reflected Characteristics of the reflected ray:

9. v 2 f 2 2 A 2 = f i, b/c it’s the same color < v 1 (given)  i, b/c = v/f Characteristics of the transmitted ray: < A 1 b/c not all energy is transmitted air (medium 1) glass (medium 2) boundary incident ray reflected ray transmitted ray Notice: f r, f i, and f 2 are ___________________________!!! exactly the same

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

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 ______________________________________________________. n = c/v absolute index of refraction, in a vacuum, c, in the material, v changes remains the same also change speed of light 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. n = c / v Given:n water =1.33 c = 3.00 x 10 8 m/s Unknown: v = ? 1.33 = (3.00 x 10 8 m/s) / v v = 2.26 x 10 8 m/s

15. To compare the speeds and wavelengths of two materials, use the equation: higher n  __________________  __________________ slower speed shorter wavelength n2n2 n1n1 v2v2 v1v1 2 1 = = Ex: what is the relationship between v and n? v n = c / v n

16. Physics Reference Tables, page 5, top:

17. 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 n2n2 n1n1 2 v2v2 v1v1 1 = = 1.55 1.00 2 780. nm = n1n1 n2n2 air CD laser Given: 2 = ? 1 = 780. nm n 1 = 1.00 n 2 = 1.55 Unknown: 2 = 780. nm/1.55 2 = 503 nm

18. Ex: Laser light entering a CD:     shorter  can read more data