PHYS 15 Optics
Week #1 – Reflection and refraction
Assignment due February 15, 2021
Reading: Wolfson and Pasachoff, Sections 35:1 - 35:4
Note: In Wolfson and Pasachoff there are Questions and Problems in the text. These are all
Problems on the weekly problem set.
1. An electromagnetic wave follows the mathematical form E(x, t) = E0 cos(kx − ωt + φ). It has
an amplitude E0 equal to 2 N/C, a wavelength of 6 m, and a period of 20 ns.
(a) What is the velocity of the wave?
(b) What is the wavevector k of the wave?
(c) What is the angular frequency ω of the wave?
2. Wolfson and Pasachoff, Problem 35-4
Draw a ray diagram showing the path of the light, making clear the direction of the outgoing
ray.
3. Wolfson and Pasachoff, Problem 35-16
4. Wolfson and Pasachoff, Problem 35-30
The prism in Fig. 35-15a has angles of 45◦ , 45◦ , and 90◦ .
n2
In the ray diagram of the figure on the right, the ray
is incident at the critical angle on the interface between
5.
materials 2 and 3. Angle φ = 60.0◦ , and two of the
indices of refraction are n1 = 1.70 and n2 = 1.60.
n3
Φ
θ
n1
(a) Find index of refraction n3 .
(b) Find angle θ.
(c) If θ is decreased, does light refract into material 3? Please explain.
In the figure on the right, an22.00 m long vertical pole
extends from the bottom of a swimming pool to a point
50.0 cm above the water. Rays of sunlight are incident
n3
6.
Φ What is the
at angle θ = 55.0◦ with the horizontal.
length of the shadow of the pole on the level bottom of
θ
the pool?
n1
B
1
A
C
Blocked
sunrays
θ