Beats — NEET & JEE Questions

Question 1 · difficulty L1 · recall

The beat frequency produced by two sound waves of frequencies $f_1$ and $f_2$ is

• A. $|f_1-f_2|$
• B. $f_1+f_2$
• C. $f_1f_2$
• D. $(f_1+f_2)/2$

Question 2 · difficulty L2 · understanding

Beats are heard because of

• A. periodic variation of resultant amplitude due to superposition of nearby frequencies
• B. reflection only
• C. dispersion only
• D. constant destructive interference

Question 3 · difficulty L2 · understanding

If two tuning forks have exactly equal frequencies, the beat frequency is

• A. zero
• B. equal to either frequency
• C. double either frequency
• D. infinite

Question 4 · difficulty L2 · understanding

For clearly distinguishable beats, the two frequencies should generally be

• A. close to each other
• B. extremely far apart
• C. exactly zero
• D. one ultrasonic and one infrasonic only

Question 5 · difficulty L3 · application

Two tuning forks of frequencies 256 Hz and 260 Hz are sounded together. What beat frequency is heard?

• A. 2 Hz
• B. 4 Hz
• C. 8 Hz
• D. 516 Hz

Question 6 · difficulty L3 · application

A 300 Hz fork produces 5 beats per second with an unknown fork. Which frequencies are possible for the unknown fork?

• A. 295 Hz or 305 Hz
• B. 300 Hz only
• C. 150 Hz or 600 Hz
• D. 5 Hz or 60 Hz

Question 7 · difficulty L3 · application

Two sounds produce 8 beats per second. If one frequency is 512 Hz, which could be the other frequency?

• A. 504 Hz
• B. 508 Hz
• C. 516 Hz
• D. Both A and a frequency of 520 Hz would work

Question 8 · difficulty L3 · application

Two tuning forks produce 6 beats per second. If one fork is slightly loaded so that its frequency decreases and the beat frequency becomes 2 Hz, what happened to the frequency difference?

• A. It decreased from 6 Hz to 2 Hz
• B. It increased from 2 Hz to 6 Hz
• C. It stayed 6 Hz
• D. It became zero

Question 9 · difficulty L4 · application

A 400 Hz fork gives 6 beats per second with an unknown fork. When wax is added to the unknown fork, the beat frequency becomes 2 Hz. What was the unknown fork's original frequency?

• A. 394 Hz
• B. 406 Hz
• C. 398 Hz
• D. 402 Hz

Question 10 · difficulty L4 · application

A 500 Hz fork and an unknown fork produce 4 beats per second. Filing the unknown fork slightly increases its frequency, and the beats disappear. What was its initial frequency?

• A. 496 Hz
• B. 500 Hz
• C. 504 Hz
• D. 508 Hz