Question 1

A wave pulse traveling to the right along a thin cord reaches a discontinuity where the rope becomes thinner and lighter. What is the orientation of the reflected and transmitted pulses?

Accepted Answer

A)  Both pulses are right side up. 
B)  The reflected pulse returns right side up while the transmitted pulse is inverted. 
C)  The reflected pulse returns inverted while the transmitted pulse is right side up. 
D)  Both pulses are inverted.

Question 2

Consider a pipe of length L that is open at both ends. What are the wavelengths of the three lowest-pitch tones produced by this pipe?

Accepted Answer

A)  4L, 2L, L 
B)  2L, L, L/2 
C)  2L, L, 2L/3 
D)  4L, 4L/3, 4L/5 
E)  2.0L, L, L/2

Question 3

A wave pulse traveling to the right along a thin cord reaches a discontinuity where the rope becomes thicker and heavier. What is the orientation of the reflected and transmitted pulses?

Accepted Answer

A)  Both pulses are right side up. 
B)  The reflected pulse returns right side up while the transmitted pulse is inverted. 
C)  The reflected pulse returns inverted while the transmitted pulse is right side up. 
D)  Both pulses are inverted.

Question 4

A 2.0-m string is fixed at both ends and tightened until the wave speed is 78 m/s. What is the frequency of the standing wave shown in the figure?

Accepted Answer

A)  120 Hz 
B)  230 Hz 
C)  350 Hz 
D)  470 Hz

Question 5

Two loudspeakers placed 6.0 m apart are driven in phase by an audio oscillator whose frequency range is 2193 Hz to 2967 Hz. A point P is located 4.4 m from one loudspeaker and 3.6 m from the other. The speed of sound is 344 m/s. The frequency produced by the oscillator, for which constructive interference of sound occurs at point P, is closest to

Accepted Answer

A)  2580 Hz. 
B)  2903 Hz. 
C)  2473 Hz. 
D)  2795 Hz. 
E)  2688 Hz.

Question 6

A carousel that is 5.00 m in radius has a pair of 600-Hz sirens mounted on posts at opposite ends of a diameter. The carousel rotates with an angular velocity of 0.800 rad/s. A stationary listener is located at a distance from the carousel. The speed of sound is 350 m/s. The maximum beat frequency of the sirens at the position of the listener is closest to

Accepted Answer

A)  6 Hz. 
B)  8 Hz. 
C)  10 Hz. 
D)  12 Hz. 
E)  14 Hz.

Question 7

One of the harmonics of a column of air open at one end and closed at the other has a frequency of 448 Hz and the next higher harmonic has a frequency of 576 Hz. What is the fundamental frequency of the air column?

Accepted Answer

A)  32 Hz 
B)  64 Hz 
C)  88 Hz 
D)  128 Hz 
E)  256 Hz

Question 8

A violin with string length 32 cm and string density 1.5 g/cm resonates with the first overtone from a 2.0-m long organ pipe with one end closed and the other end open. What is the tension in the string?

Accepted Answer

A)  1000 N 
B)  110 N 
C)  450 N 
D)  4100 N 
E)  56 N

Question 9

A heavy stone of mass m is hung from the ceiling by a thin 8.25-g wire that is 65.0 cm long. When you gently pluck the upper end of the wire, a pulse travels down the wire and returns 7.84 ms later, having reflected off the lower end. The speed of sound in the room is 344 m/s, and the stone is heavy enough to prevent the lower end of the wire from moving. If the wire is vibrating in its second overtone, what is the wavelength of the sound it will produce?

Accepted Answer

A)  0.217 m 
B)  0.433 m 
C)  0.650 m 
D)  0.899 m 
E)  1.35 m

Question 10

Light of wavelength 425.0 nm in air falls at normal incidence on an oil film that is 850.0 nm thick. The oil is floating on a water layer 15 cm thick. The refractive index of water is 1.33, and that of the oil is 1.40. You want to add oil so that light reflected off of the top of the oil film will be canceled. What is the minimum distance that you should INCREASE the oil film?

Accepted Answer

A)  60.7 nm 
B)  75.9 nm 
C)  106 nm 
D)  121 nm 
E)  152 nm

Question 11

50) A 0.25-m string, vibrating in its sixth harmonic, excites a 0.96-m pipe that is open at both ends into its second overtone resonance. The speed of sound in air is 345 m/s. The common resonant frequency of the string and the pipe is closest to

Accepted Answer

A)  540 Hz. 
B)  360 Hz. 
C)  450 Hz. 
D)  630 Hz. 
E)  700 Hz.

Question 12

A 360-nm thick oil film floats on the surface of the water. The indices of refraction of the oil and the water are 1.5 and 1.33, respectively. The surface of the oil is illuminated from above at normal incidence with white light. What TWO wavelengths of light in the 400-nm to 800-nm wavelength band are most strongly reflected?

Accepted Answer

A)  410 nm and 700 nm 
B)  430 nm and 720 nm 
C)  450 nm and 740 nm 
D)  470 nm and 760 nm 
E)  490 nm and 780 nm

Question 13

A puddle of water has a thin film of gasoline floating on it. A beam of light is shining perpendicular on the film. If the wavelength of light incident on the film is 560 nm and the indices of refraction of gasoline and water are 1.40 and 1.33, respectively, what is the minimum thickness of the film to see a bright reflection?

Accepted Answer

A)  100 nm 
B)  200 nm 
C)  300 nm 
D)  400 nm 
E)  500 nm

Question 14

Two extremely flat glass plates, 10.0 cm wide, touch at one end but are separated by a thin wire at the other end, forming a wedge. Light with a wavelength of 450 nm shines almost perpendicularly on the glass and forms fringes which are 1.80 mm apart. What is the diameter of the wire?

Accepted Answer

A)  25.0 µm 
B)  17.5 µm 
C)  20.0 µm 
D)  12.5 µm 
E)  10.0 µm

Question 15

In a resonating pipe that is open at one end and closed at the other end, there

Accepted Answer

A)  are displacement nodes at each end. 
B)  are displacement antinodes at each end. 
C)  is a displacement node at the open end and a displacement antinode at the closed end. 
D)  is a displacement node at the closed end and a displacement antinode at the open end.

Question 16

What characteristic of sound determines the "pitch" of a musical note?

Accepted Answer

A)  amplitude 
B)  wavelength 
C)  frequency 
D)  phase 
E)  intensity

Question 17

Light of frequency 6.00 × 1014 Hz illuminates a soap film (n = 1.33) having air on both sides of it. When viewing the film by reflected light, what is the minimum thickness of the film that will give an interference maximum when the light is incident normally on it? (c = 3.00 × 108 m/s)

Accepted Answer

A)  24.0 nm 
B)  94.0 nm 
C)  188 nm 
D)  279 nm 
E)  376 nm

Question 18

Standing waves of frequency 57 Hz are produced on a string that has mass per unit length 0.0160 kg/m. With what tension must the string be stretched between two supports if adjacent nodes in the standing wave are to be 0.71 meters apart?

Accepted Answer

The answer of Standing waves of frequency 57 Hz are...

Question 19

A policeman in a stationary car measures the speed of approaching cars by means of an ultrasonic device that emits a sound with a frequency of 41.2 kHz. A car is approaching him at a speed of 33.0 m/s. The wave is reflected by the car and interferes with the emitted sound producing beats. What is the frequency of the beats? The speed of sound in air is 330 m/s.

Accepted Answer

A)  9.2 kHz 
B)  4.1 kHz 
C)  4.6 kHz 
D)  1.2 kHz 
E)  8.2 kHz

Question 20

A guitar string 0.650 m long has a tension of 61.0 N and a mass per unit length of 3.00 g/m.
(a) What is the speed of waves on the string when it is plucked?
(b) What is the string's fundamental frequency of vibration when plucked?

Accepted Answer

The answer of A guitar string 0.650 m long has...

Exam 21: Superpositions