Quiz #5

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Multiple choice: 1 pt. each

1. A police car is driving north with it's siren on. A car in front of the police car is also driving north. The driver of the car hears the siren

A. at a higher frequency than the actual frequency of the siren.

B. at a lower frequency than the actual frequency of the siren.

C. at the actual frequency of the siren.

* D. at an unknown frequency. We need to know the speeds of both cars.

2. Standing waves result from the interference of two waves

A. traveling in opposite directions with the same amplitude, frequency, and wavelength.

* B. traveling in the same direction with the same amplitude, frequency, and wavelength.

C. traveling in opposite directions with not necessarily the same amplitude, frequency, and wavelength.

D. traveling in the same direction with not necessarily the same amplitude, frequency, and wavelength.

3. Two traveling waves with the same wavelength interfere destructively at a point if the phases (the argument in the or ) differ by

A. 0 m

B.

* C.

D.

4. A string of length L vibrates at its second harmonic (the first harmonic is the fundamental one, i.e. the lowest vibration frequency). How many nodes are there along the string (not including the end points of the string)?

A. none

* B. one

C. two

D. Not enough information given.

5. Which of the following is NOT true about electromagnetic waves?

A. The oscillating magnetic and electric fields are always perpendicular to each other.

B. They obey the superposition principle (algebraic addition of waves).

* C. The are always visible to the human eye.

D. No medium is necessary in order for them to exist.

6. A disk is painted black on one side and metallic (shiny) on the other. The disk is oriented so that the black side is facing you. If an equal intensity of light impinges upon each side of the disk,

* A. there is a net pressure exerted on the disk toward you.

B. there is a net pressure exerted on the disk away from you.

C. there is no net pressure exerted on the disk.

D. there is no pressure exerted on either face because light can't exert pressure.

7. A transverse wave on a string is described by .

a) What is the maxiumum transverse displacement of a point on the string? (1 pt.)

b) What is the maximum velocity of a point on the string? (1 pt.)

c) What is the maximum acceleration of a point on the string? (1 pt.)

d) What is the phase speed (speed of the wave itself)? (1 pt.)