Waves · Question 36

A tuning fork of frequency 512 Hz makes 4 beats per second with the vibrating string of a piano. The beat frequency decreases to 2 beats per sec when the tension in the piano string is slightly increased. The frequency of the piano string before increasing the tension was

1. 510 Hz
2. 514 Hz
3. 516 Hz
4. 508 Hz

Each of the two strings of length 51.6 cm and 49.1 cm are tensioned separately by 20 N force. Mass per unit length of both the strings is same and equal to 1 g/m. When both the strings vibrate simultaneously the number of beats is

1. 7
2. 8
3. 3
4. 5

A wave in a string has an amplitude of 2 cm. The wave travels in the +ve direction of x axis with a speed of 128 m/s and it is noted that 5 complete waves fit in 4 m length of the string. The equation describing the wave is

1. y = (0.02) m sin (15.7x - 2010t)
2. y = (0.02) m sin (15.7x + 2010t)
3. y = (0.02) m sin (7.85x - 1005t)
4. y = (0.02) m sin (7.85x + 1005t)

The driver of a car travelling with speed 30 m/s towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 m/s, the frequency of reflected sound as heard by driver is

1. 555.5 Hz
2. 720 Hz
3. 500 Hz
4. 550 Hz

Two periodic waves of intensities I1 and I2 pass through a region at the same time in the same direction. The sum of the maximum and minimum intensities is

1. ( I1 - I2 )2
2. 2 (I1 + I2 )
3. I1 + I2
4. ( I1 + I2 )2

The wave described by y = 0.25 sin(10 x - 2 t), where x and y are in metres and t in seconds, is a wave travelling along the

1. +ve x direction with frequency 1 Hz and wavelength = 0.2 m.
2. -ve x direction with amplitude 0.25 m and wavelength = 0.2 m.
3. -ve x direction with frequency 1 Hz.
4. +ve x direction with frequency Hz and wavelength = 0.2 m.

Two vibrating tuning forks produce waves given by y1 = 4 500 t and y2 = 2 506 t. Number of beats produced per minute is

1. 360
2. 180
3. 60
4. 3

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