11.

The driver of a car travelling with speed 30 ms^-1 towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 ms^-1, the frequency of reflected sound as heard by driver is

• 550 Hz

• 555.5 Hz

• 720 Hz

• 720 Hz

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

• - ve x direction with frequency 1 Hz

• +ve x direction with frequency π  Hz and wavelength λ = 0.2 m

• +ve x direction with frequency 1 Hz and wavelength λ = 0.2 m

• +ve x direction with frequency 1 Hz and wavelength λ = 0.2 m

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

• 12

• 0

• 1

• 1

A transverse wave propagating along x-axis is represented by:


where x is in metres and t is in seconds. The speed of the wave is

•  m/s
• 
• 
• 

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?

• 2

• 4

• 
• 

Which one of the following statements is true?

• Both light and sound waves in air are transverse

• The sound waves in air are longitudinal while the light waves are transverse

• Both light and sound waves in air are longitudinal

• Both light and sound waves in air are longitudinal

The two nearest harmonics of a tube closed at one end and open at other end are 220 Hz and 260 Hz. What is the fundamental frequency of the system?

• 10 Hz

• 20 Hz

• 30 Hz

• 30 Hz

Two soap bubbles coalesce. It is noticed that whilst joined together, the raddii of the bubbles are a and b where a>b. Then the radius of curvature of the interface between the two bubbles will be

• a-b

• a+b

• ab/(a-b)

• ab/(a+b)

If vibration of string is to be two times, then tension in the string must be made

• Eight times

• Four times

• Twice

• Half

A siren emitting sound of frequency 500 Hz is going away from a stationary listener with a speed of 50 m/s, the frequency of sound heard directly from the siren is 

• 286.5 HZ

• 481 Hz

• 434.2 Hz

• 580 Hz