Apparent Frequency:Listener Moving

Q. A source is moving along a circle given by the equation x2 + y2 = R2, with cons†an t speed , in anti-clockwise sense. A detector is at rest at point (2R, 0) w.r.t. the centre of the circle. If the frequency emitted by the source is f and the speed of sound, C = 330 m/s. Then the position of the source when the detecter records maximum and minimum frequencies and the value of min and max frequencies.

Q. A person riding on a merry-go-round emits a sound wave of a certain frequency. Does a person at the centre observe the Doppler effect?

1. Yes
2. No

Q. A SONAR system fixed in a submarine operates at a frequency 40.0 kHz. An enemy submarine moves towards the SONAR with a speed of 360 km h¯¹. What is the frequency of sound reflected by the submarine ? Take the speed of sound in water to be 1450 m s¯¹.

Q. The engine of a train sounds a whistle at frequency $\left(f\right)$. The frequency heard by a passenger is

1. $\frac{1}{f}$
2. $>f$
3. $<f$
4. $f$

Q. Two cars moving in opposite directions approach each other with speeds of $40{\text{ms}}^{-1}$ and $50{\text{ms}}^{-1}$ respectively. The driver of the first car blows a horn of frequency $400\text{Hz}$. The frequency heard by the driver of the second car is
[speed of sound $=340{\text{ms}}^{-1}$]

1. $515\text{Hz}$
2. $375\text{Hz}$
3. $520\text{Hz}$
4. $450\text{Hz}$

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.

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

1. 

2. 

3. 

4. 2

Q. An observer travelling with a constant velocity of $20m{s}^{-1}$ passes close to a stationary source of sound and notices that there is a change of frequency of $50H_Z$ as he passes the source. What is the frequency of the source? Speed of sound in air = 340 m/s.

1. 450 Hz
2. 425 Hz
3. 400 Hz
4. 500 Hz

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 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

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. $\frac{19}{18}$

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. $\frac{19}{18}$

Q. Doppler shift in frequency does not depend upon

1. the frequency of wave produced
2. the speed of the source
3. distance between source and observer
4. the speed of the observer

Q. A source of sound S has a frequency $f$. Wind is blowing from source to observer O with velocity $u$. If speed of sound with respect to air is $C$, the wavelength of sound detected by O is:

1. $\frac{C+u}{f}$
2. $\frac{C-u}{f}$
3. $\frac{C(C+u)}{(C-u)f}$
4. $\frac{C}{f}$