Waves · Question 43

Two sound waves with wavelengths 5.0 m and 5.5 m respectively, each propagate in a gas with velocity 330 m/s. We expect the following number of beats per second.

1. 6
2. 12
3. 0
4. 1

The time of reverberation of a room A is one second. What will be the time (in seconds) of reverberation of a room, having all the dimensions double of those of room A?

1. 1
2. 2
3. 4
4. 1/2

A transverse wave propagating along x-axis is represented by y(x, t) = 8.0 (0.5 x - 4 t - /4) where x is in metres and t is in seconds. The speed of the wave is

1. 8 m/s
2. 4 m/s
3. 0.5 m/s
4. /4 m/s

Which one of the following statements is true?

1. Both light and sound waves can travel in vacuum
2. Both light and sound waves in air are transverse
3. The sound waves in air are longitudinal while the light waves are transverse
4. Both light and sound waves in air are longitudinal

A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distances of 2 m and 3 m respectively from the source. The ratio of the intensities of the waves at P and Q is

1. 3 : 2
2. 2 : 3
3. 9 : 4
4. 4 : 9

The phase difference between two waves represented by y1 = 10-6 [100t + (x/50) + 0.5] m y2 = 10-6 [100t + (x/50)] m, where x is expressed in metres and t is expressed in seconds, is approximately

1. 1.07 radians
2. 2.07 radians
3. 0.5 radians
4. 1.5 radians

A car is moving towards a high cliff. The driver sounds a horn of frequency f. The reflected sound heard by the driver has frequency 2f. If v is the velocity of sound, then the velocity of the car, in the same velocity units, will be

1. v/ 2
2. v/3
3. v/4
4. v/2

An observer moves towards a stationary source of sound with a speed 1/5th of the speed of sound. The wavelength and frequency of the source emitted are and f respectively. The apparent frequency and wavelength recorded by the observer are respectively

1. 1.2f, 1.2
2. 1.2f,
3. f, 1.2
4. 0.8f, 0.8

A wave travelling in positive X-direction with a = 0.2 m, velocity = 360 m s-1 and = 60 m, then correct expression for the wave is

1. y = 0.2 [2 (6t + x60 ) ]
2. y = 0.2 [ (6t + x60 ) ]
3. y = 0.2 [2 (6t - x60 ) ]
4. y = 0.2 [ (6t - x60 ) ]

A whistle revolves in a circle with angular speed = 20 rad/s using a string of length 50 cm. If the frequency of sound from the whistle is 385 Hz, then what is the minimum frequency heard by an observer which is far away from the centre (velocity of sound = 340 m/s)

1. 385 Hz
2. 374 Hz
3. 394 Hz
4. 333 Hz