Wave Properties

A student is using a loudspeaker to generate sound waves. The loudspeaker can be used to generate different sound waves at the same frequency f0. The loudspeaker first produces an amount of energy E1 in a time interval Δt0 to generate Sound Wave 1, which has an amplitude A1. The loudspeaker then produces an amount of energy E2 in the same time interval Δt0 to generate Sound Wave 2, which has an amplitude A2. If Sound Wave 2 is louder than Sound Wave 1, which of the following correctly compares A1 to A2 and E1 to E2?

A) A

B) B

C) C

D) D

D) D

Since Sound Wave 2 is louder than Sound Wave 1, then we know the A2 has to be greater than A1, eliminating choices A and B.

Energy is also equal to A² so it is directly proportional to each other. Therefore, E2 has to be greater than E1, eliminating answer choice A.

A) (L_X = L_Y) > L_Z

B) L_Y > (L_X = L_Z)

C) L_Y > L_X > L_Z

D) L_Z > L_X > L_Y

B) L_Y > (L_X = L_Z)

The greater the amplitude, the louder the sound. Based off of the table, L_X and L_Z are equal to each other therefore the are the same amount of loud. Since L_Y is greater than both then the only correct answer choice is B.

The figure shows two wave pulses, 1 and 2, traveling to the right along the same string. Wave Pulse 1 has a greater amplitude than Wave Pulse 2. Which of the following claims about the two wave pulses is true?

A) The direction of the disturbance is parallel to the direction of propagation of the wave for both wave pulses.

B) Wave Pulse 1 carries more energy than Wave Pulse 2.

C) Wave Pulse 1 transfers more matter along the string than Wave Pulse 2.

D) The speed at which Wave Pulse 1 propagates along the string is greater than the speed at which Wave Pulse 2 propagates along the string.

B) Wave Pulse 1 carries more energy than Wave Pulse 2.

Energy = (Amplitude)²

Therefore, since Wave Pulse 1 has a greater amplitude then it is going to have more energy than Wave Pulse 2.

A wave generator can produce wave pulses of different amplitudes on a string that has a fixed amount of tension. A student claims that increasing the amplitude of the wave pulses will cause the speed at which the pulses propagate along the string to increase. Is the student’s claim correct? Why or why not?

A) Yes. Increasing the amplitude of a wave pulse increases the energy carried by the pulse.

B) Yes. Increasing the amplitude of a wave pulse causes points on the string to move a greater distance in the same amount of time.

C) No. The speed at which a wave pulse propagates along a string is independent of the amplitude of the wave.

D) No. The speed at which a wave pulse propagates along a string is inversely related to the amplitude of the wave.

C) No. The speed at which a wave pulse propagates along a string is independent of the amplitude of the wave.

We know that the amplitude doesn”t increase the speed in any way. Therefore, the only correct answer is C.