How do these work?

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

When light passes into a denser medium, it__________________. slows down c = 3.0 x 108 m/s a/ In vacuum: v = ___________________ molecules b/ In water: 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

Ex. Light passing from air into glass : ________________ 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)

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)

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 ___________________________!!!

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

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.

Physics Reference Tables, page 5, top:

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

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

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

Physics Reference Tables, page 5, top:

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 n2 CD Given: n2 n1 l2 v2 v1 l1 = l1 = 780. nm n1 = 1.00 1.55 780. nm n2 = 1.55 = 1.00 l2 Unknown: l2 = 780. nm/1.55 l2 = ? l2 = 503 nm

Ex: Laser light entering a CD:  shorter  can read more data