The Ultimate Interference and Superposition Quiz

1. A police car turns on its siren as it is driving away from you. What happens to the sound pitch?

The pitch will sound lower.

You will be unable to hear the pitch.

The pitch will sound higher.

There is insufficient information to tell.

When a police car is driving away from you and turns on its siren, the sound waves it produces are stretched out or lengthened due to the Doppler effect. This causes the frequency of the sound waves to decrease, resulting in a lower pitch. Therefore, the pitch of the siren will sound lower as the police car moves away from you.

Explanation

When a police car is driving away from you and turns on its siren, the sound waves it produces are stretched out or lengthened due to the Doppler effect. This causes the frequency of the sound waves to decrease, resulting in a lower pitch. Therefore, the pitch of the siren will sound lower as the police car moves away from you.

2. Two waves, one with an amplitude of 1.2m and the other of 0.78m are superimposed with destructive interference. What is the resultant amplitude?

0m

0.42m

0.65m

1.98m

When two waves superimpose with destructive interference, the amplitudes of the waves cancel each other out. In this case, the amplitude of one wave is 1.2m and the amplitude of the other wave is 0.78m. Since they are superimposed with destructive interference, the resultant amplitude is the difference between the two amplitudes, which is 1.2m - 0.78m = 0.42m. Therefore, the correct answer is 0.42m.

Explanation

When two waves superimpose with destructive interference, the amplitudes of the waves cancel each other out. In this case, the amplitude of one wave is 1.2m and the amplitude of the other wave is 0.78m. Since they are superimposed with destructive interference, the resultant amplitude is the difference between the two amplitudes, which is 1.2m - 0.78m = 0.42m. Therefore, the correct answer is 0.42m.

3. Two waves, each with an amplitude of 0.5m are superimposed with constructive interference such that they are in phase. What is the resultant amplitude?

0.25m

0.50m

1m

1.25m

When two waves superimpose with constructive interference, their amplitudes add up. Since both waves have an amplitude of 0.5m and they are in phase, their amplitudes will simply add together. Therefore, the resultant amplitude will be 0.5m + 0.5m = 1m.

Explanation

When two waves superimpose with constructive interference, their amplitudes add up. Since both waves have an amplitude of 0.5m and they are in phase, their amplitudes will simply add together. Therefore, the resultant amplitude will be 0.5m + 0.5m = 1m.

4. A piano tuner hears one beat every 2.0s when trying to adjust two strings, one of which is sounding 350Hz. How far off in frequency is the other string?

0.5Hz

1Hz

2Hz

4Hz

The piano tuner hears one beat every 2.0s, which indicates that there is a difference in frequency between the two strings. Since one of the strings is sounding at 350Hz, the other string must be slightly off in frequency. The difference in frequency can be calculated by dividing the number of beats per second (1 beat every 2.0s) by the number of beats per cycle (2 beats per cycle). Therefore, the other string is 0.5Hz off in frequency.

Explanation

The piano tuner hears one beat every 2.0s, which indicates that there is a difference in frequency between the two strings. Since one of the strings is sounding at 350Hz, the other string must be slightly off in frequency. The difference in frequency can be calculated by dividing the number of beats per second (1 beat every 2.0s) by the number of beats per cycle (2 beats per cycle). Therefore, the other string is 0.5Hz off in frequency.

5. If waves overlap and are in phase, how will that affect the resultant wave?

Increase the amplitude

Decrease the amplitude

Increase the frequency

Decrease the frequency

When waves overlap and are in phase, it means that their crests and troughs align perfectly. This results in constructive interference, where the amplitudes of the waves add up. As a result, the amplitude of the resultant wave increases.

Explanation

When waves overlap and are in phase, it means that their crests and troughs align perfectly. This results in constructive interference, where the amplitudes of the waves add up. As a result, the amplitude of the resultant wave increases.

6. Two identical waves are superimposed with destructive interference. What will happen to the resulting wave?

It will be still. There will be no wave.

The two waves will pass through each other without problem.

It will be half as large as each original wave.

It will be twice as large as each original wave.

When two identical waves superimpose with destructive interference, they cancel each other out. This means that the crests of one wave align with the troughs of the other wave, resulting in a wave with zero amplitude. Therefore, the resulting wave will be still and there will be no wave.

Explanation

When two identical waves superimpose with destructive interference, they cancel each other out. This means that the crests of one wave align with the troughs of the other wave, resulting in a wave with zero amplitude. Therefore, the resulting wave will be still and there will be no wave.

7. If waves overlap and are out of phase, how will that affect the resultant wave?

Decrease the frequency

Increase the amplitude

Decrease the amplitude

Increase the frequency

When waves overlap and are out of phase, it means that the peaks of one wave align with the troughs of the other wave. This causes destructive interference, where the waves cancel each other out. As a result, the amplitude of the resultant wave decreases.

Explanation

When waves overlap and are out of phase, it means that the peaks of one wave align with the troughs of the other wave. This causes destructive interference, where the waves cancel each other out. As a result, the amplitude of the resultant wave decreases.

8. The siren of an ambulance at rest emits a frequency of about 1600Hz. What frequency will you hear if you are at rest and the ambulance moves 30m/s away from you?

150Hz

1320Hz

1470Hz

1600Hz

As the ambulance is moving away from you, the sound waves emitted by the siren will experience a Doppler shift. The frequency of the sound waves will appear lower to you because the source is moving away. The formula for the Doppler effect is given by: observed frequency = source frequency * (speed of sound + speed of observer) / (speed of sound + speed of source). Plugging in the given values, we get: observed frequency = 1600Hz * (343m/s + 30m/s) / (343m/s + 0m/s) = 1470Hz. Therefore, the frequency you will hear is 1470Hz.

Explanation

As the ambulance is moving away from you, the sound waves emitted by the siren will experience a Doppler shift. The frequency of the sound waves will appear lower to you because the source is moving away. The formula for the Doppler effect is given by: observed frequency = source frequency * (speed of sound + speed of observer) / (speed of sound + speed of source). Plugging in the given values, we get: observed frequency = 1600Hz * (343m/s + 30m/s) / (343m/s + 0m/s) = 1470Hz. Therefore, the frequency you will hear is 1470Hz.

9. Resonance in a system, such as a string fixed on both ends, occurs when

It is oscillating in simple harmonic motion.

Its frequency is smaller than the frequency of an external source.

Its frequency is greater than the frequency of an external source.

Its frequency is the same as the frequency of an external source.

When resonance occurs in a system, such as a string fixed on both ends, it means that the system is vibrating at the same frequency as an external source. This happens when the natural frequency of the system matches the frequency of the external source, causing the system to oscillate with maximum amplitude. Resonance can lead to amplification of vibrations and is often observed in musical instruments, where the vibrations of a string or air column are matched to the frequency of a specific note being played.

Explanation

When resonance occurs in a system, such as a string fixed on both ends, it means that the system is vibrating at the same frequency as an external source. This happens when the natural frequency of the system matches the frequency of the external source, causing the system to oscillate with maximum amplitude. Resonance can lead to amplification of vibrations and is often observed in musical instruments, where the vibrations of a string or air column are matched to the frequency of a specific note being played.

10. Two pure tones are sounded together, and a particular beat frequency is heard. What happens to the beat frequency if the frequency of one of the tones is increased?

It increases.

It decreases.

It could either increase or decrease.

It does not change.

When two pure tones are sounded together, a beat frequency is heard. This beat frequency is the difference between the frequencies of the two tones. If the frequency of one of the tones is increased, the difference between the frequencies will also increase, resulting in a higher beat frequency. However, depending on the specific frequencies of the tones, it is also possible for the beat frequency to decrease if the increase in frequency is not significant enough to overcome the original difference. Therefore, the beat frequency could either increase or decrease when the frequency of one of the tones is increased.

Explanation

When two pure tones are sounded together, a beat frequency is heard. This beat frequency is the difference between the frequencies of the two tones. If the frequency of one of the tones is increased, the difference between the frequencies will also increase, resulting in a higher beat frequency. However, depending on the specific frequencies of the tones, it is also possible for the beat frequency to decrease if the increase in frequency is not significant enough to overcome the original difference. Therefore, the beat frequency could either increase or decrease when the frequency of one of the tones is increased.