Beat Frequency

Q.

Two tuning forks when sounded together produced a beat with frequency of 4 Hz. The frequency of one fork is 256 Hz. The number of beats heard increases when the fork of frequency 256 Hz is loaded with wax. The frequency of the other fork is,

1. 504

2. 520

3. 252

4. 260

Q. Two factories are sounding their sirens at 800 Hz. A man goes from one factory to the other at a speed of 2 m/s. The velocity of sound is 320 m/s. The number of beats heard by the person in 1 s will be

1. 2
2. 4
3. 8
4. 10

Q. One train is approaching an observer at rest and another train is receding from him with the same velocity 4 m/s. Both the trains blow whistles of same frequency of 243 Hz. The beat frequency in Hz as heard by the observer is (speed of sound in air is 320 m/s)

1. 6
2. 4
3. 1
4. 10

Q. A car emitting sound of frequency 500 Hz speeds towards a fixed wall at 4 m/s. An observer in the car hears both the source frequency as well as the frequency of sound reflected from the wall. If he hears 10 beats per second between the two sounds, the velocity of sound in air will be

1. 330 m/s
2. 404 m/s
3. 340 m/s
4. 387 m/s

Q. A piano wire B vibrates at a fundamental frequency of 600 Hz. A second identical wire A produces 6 beats per second with it when the tension in A is slightly increased. Find the ratio of the tension in A to the tension in B.

1. 1.02

2. 0.5

3. 2

4. 3

Q. Two sources A and B are sounding notes of frequency 680 Hz. A listener moves from A to B with a constant velocity u. If the speed of sound is 340 m/s, what must be the value of u so that he hears
10 beats per second?

1. 2.0 m/s
2. 2.5 m/s
3. 30 m/s
4. 3.5 m/s

Q.

Calculate the frequency of beats produced in air when two sources of sound are activated, one emitting a wavelength of 32 cm and the other of 32.2 cm. The speed of sound in air is 350 m/s.

1. 20 Hz

2. 10 Hz

3. 2 Hz

4. 7 Hz

Q. A tuning fork produces 4 beats per second with another tuning fork of frequency 256 Hz. The first one is now loaded with a little wax and the beat frequency is found to increase to 6 per second. What was the original frequency of the tuning fork?

1. 252 Hz

2. 260 Hz

3. 262 Hz

4. 250 Hz

Q.

A bus is moving with a velocity of 5 m/s towards a huge wall. the driver sounds a horn of frequency 165 Hz. If the speed of sound in air is 355 m/s, the number of beats heard per second by a passenger on the bus will be approximately,

1. 6

2. 5

3. 4

4. 3

Q. Two sound sources are moving in opposite directions with velocities $v_1$ and $v_2(v_1>v_2)$. Both are moving away from a stationary observer. The frequency of both the sources is 900 Hz. What is the value of $v_1–v_2$ so that the beat frequency observed by the observer is 6 Hz? Speed of sound v = 300 m/s. Given that $v_1$ and $v_2$ ≪ v.

1. 1 m/s
2. 2 m/s
3. 3 m/s
4. 4 m/s