AP Physics Physics: Waves & Optics 2

Question 1

A wave on a string has a frequency of 4 Hz and a wavelength of 0.5 m. What is the wave speed?

Accepted Answer

2 m/s

Answer

Wave speed v = fλ = 4 Hz × 0.5 m = 2 m/s.

Question 2

Which phenomenon explains why a straw appears bent when placed in a glass of water?

Accepted Answer

Refraction

Answer

Refraction occurs when light changes speed at the water-air interface, bending the apparent position of the straw.

Question 3

Two identical waves traveling in opposite directions on a string create a standing wave. The distance between two adjacent nodes is 0.3 m. What is the wavelength of the original traveling waves?

Accepted Answer

0.6 m

Answer

Adjacent nodes are separated by λ/2, so λ = 2 × 0.3 m = 0.6 m.

Question 4

A sound source emitting 500 Hz moves toward a stationary observer at 34 m/s. If the speed of sound is 340 m/s, what frequency does the observer hear?

Accepted Answer

550 Hz

Answer

Using the Doppler formula f' = f(v/(v−vs)) = 500(340/306) ≈ 556 Hz, closest to 550 Hz.

Question 5

In a double-slit experiment, the slit separation is doubled while keeping all other variables constant. What happens to the fringe spacing?

Accepted Answer

It is halved

Answer

Fringe spacing Δy = λL/d; doubling d halves the fringe spacing.

AP Practice Test

AP Practice Test

AP Physics Physics: Waves & Optics 2