Apparent Frequency:Listener Moving

Q. An observer move towards a stationary source of sound with a velocity equal to one fifth of the velocity of sound. The apparent change in frequency is

1. $35\%$
2. $30\%$
3. $25\%$
4. $20\%$

Q. An observer moves towards a stationary source of sound with a velocity one-fifth of the velocity of sound. What is the percentage increase in the apparent frequency?

1. $5\%$
2. $20\%$
3. $0\%$
4. $0.5\%$

Q.

The velocity of sound increases by 50% when it enters a liquid from air and when it enters another liquid from the air, the increase in velocity is 150%. What is the ratio of % increase in the wavelength in two cases?

1. 1:1

2. 1:2

3. 1:4

4. 1:3

Q.

Two identical tuning forks vibrating at the same frequency 256 Hz are kept fixed at some distance apart. A listener runs between the forks at a speed of 3.0 m/s so that he approaches one tuning fork while receding from the other (figure). Find the beat frequency observed by the listener. Speed of sound in air = 332 m/s.

1. 5.2

2. 4.2

3. 4.6

4. 5.6

Q. Two sources P and Q produces notes of frequency $990\text{Hz}$ each. A listener moves from P to Q with a speed of $1{\text{ms}}^{-1}$. If the speed of sound is $330\text{m/s}$, then the number of beats heard by the listener per second is

1. $4$
2. $5$
3. $6$
4. $7$

Q. A siren is fixed at the centre of a circle and an observer is performing a uniform circular motion around the siren with constant radius. The apparent frequency heard by the observer will be

1. same as the actual frequency of siren.
2. more than the actual frequency of siren.
3. less than the actual frequency of siren.
4. sometime more and sometime less than the actual frequency of siren.

Q. A source of sound producing sound of frequency $f$ is at rest. An observer starts moving toward it at $t=0$ with a constant small acceleration. Which of the following graph best represents the variation of observed frequency $f^{\prime }$ recorded by the observer with time $t$?

1. 
2. 
3. 
4. 

Q. Two bikes moving in opposite directions approach each other with speed of $40\text{m/s}$ and $20\text{m/s}$ respectively. The first bike sounds a horn having a frequency $380\text{Hz}$. The frequency heard by the biker of the second bike is
[velocity of sound in air is $340\text{m/s}]$

1. $450\text{Hz}$
2. $460\text{Hz}$
3. $465\text{Hz}$
4. $456\text{Hz}$

Q.

Two identical tuning forks vibrating at the same frequency 256 Hz are kept fixed at some distance apart. A listener runs between the forks at a speed of 3.0 m/s so that he approaches one tuning fork while receding from the other (figure). Find the beat frequency observed by the listener. Speed of sound in air = 332 m/s.

1. 5.2

2. 4.2

3. 4.6

4. 5.6

Q. A siren is fixed at the centre of a circle and an observer is performing a uniform circular motion around the siren with constant radius. The apparent frequency heard by the observer will be

1. more than the actual frequency of siren.
2. sometime more and sometime less than the actual frequency of siren.
3. same as the actual frequency of siren.
4. less than the actual frequency of siren.

Q. A train moves towards a stationary observer with a speed of $34\text{m/s}$. The train sounds a whistle and its frequency registered by the observer is $f_1$ . If the train speed is reduced to $17\text{m/s}$, the frequency registered is $f_2$. If the speed of sound is $340\text{m/s}$, then the ratio $\frac{f_1}{f_2}$ is

1. $\frac{1}{2}$
2. $2$
3. $\frac{18}{19}$
4. $\frac{19}{18}$