Define the index of refraction: v1v1 v2v2 A B Then under refraction,

Index of refraction

1. Light changes its speed when it moves from one medium to another. This is the cause of a. reflection. b. refraction. c. propagation. d. diffraction. e. interference.

25.13 When the light in the figure passes through the glass block, it is shifted laterally by the distance d. If n = 1.76, find the value of d.

Exercise This looks like an application to the refraction formula and a bit of geometry q1q1 q2q2 q 1 -q 2 h Ld

2. When the speed of light in a transparent medium is v, its index of refraction is a. vc b. v 2 c 2 c. v/c d. c/v e. c 2 /v 2

Larger than 1 When light goes from medium 1 to medium 2 with n 1 > n 2 Total internal reflection If we increase q 1 the right hand side grows Eventually, when sin q 1 = n 2 /n 1 we get sin q 2 =1 If we increase q 1 beyond that the wave in medium 2 disappears The ray suffers total internal reflection θ c is when sinθ 2 =1 i.e. n 1 /n 2 sin θ c =1

Find the critical angle for a ray of light in glass Critical Angle Air: n 2 = 1 Glass: n 1 = >  c = 42 o Two Rt Angle Prisms No Loss of Light; use in optical instruments Fiber Optics core, n 1 clad, n 2 < n 1 n1n1 n2n2

Endoscope "Foreign Body" in the Stomach Swallowed Quarter Here is a quarter which a young man swallowed and which is lying in the stomach. These are easily removed with a wire snare or device for grasping a coin.

Why is the sky blue?

why are sunsets red?

If n depends on l we get dispersion Dispersion blue bent more than red

I scattered = λ -4 longer wavelength less scattered more scattered

Rainbows Primary 52 0 Secondar y Colors Reversed

Flat Mirrors Light rays appear to diverge from point behind mirror Law of Reflection: s =|s’| independent of viewing angle Image is Virtual; behind mirror, can’t project on screen, light rays don’t actually pass through image point h h’ Principle axes s q s’ Magnification: M = h’/h = 1 Image is Upright s s’ s

3. When light moves from a medium where its speed is higher to a different medium where its speed is slower, the refracted ray is bent a. away from the normal. b. along the normal. c. along the surface. d. perpendicular to the normal. e. toward the normal.