How many degrees of freedom the gas molecules have if, under \(\text{STP}\), the gas density \(\rho = 1.3~\text{kg/m}^3\) and the velocity of sound propagation in it is \(330~\text{ms}^{-1}\)${\mathrm{}}^{}$?
1. \(3\)       
2. \(5\)         
3. \(7\)             
4. \(8\)

A plane progressive wave cannot be represented by

1.  $\mathrm{y} = \mathrm{a} \sin \left(\mathrm{\omega t} \pm \mathrm{kx}\right)$

2.  $\mathrm{y} = \mathrm{a} \sin 2\mathrm{\pi }\left(\frac{\mathrm{t}}{\mathrm{T}}\mp \frac{\mathrm{x}}{\lambda }\right)$

3.  $\mathrm{y} = \mathrm{a} \sin \frac{2\mathrm{\pi }}{\mathrm{\lambda }} \left(\mathrm{Vt} \mp \mathrm{x}\right)$

4.  $\mathrm{y} = \mathrm{A} \log \mathrm{x} + \mathrm{B} \log \mathrm{x}$

When a wave is reflected from a denser medium the change in phase is :

1.  0

2.  $\mathrm{\pi }$

3.  $2\mathrm{\pi }$

4.  $3\mathrm{\pi }$

A source of sound moves away with the velocity of sound from a stationary observer. The frequency of the sound heard by the observer:

1. remains the same

2. is doubled

3. is halved

4. becomes infinity
 

The equation of a wave pulse travelling along x-axis is given by $y=\frac{30}{2+{\left(x-20t\right)}^2}$, x and y are in meters and t is in seconds. The amplitude of the wave pulse is 

1.  5 m

2.  20 m

3.  15 m

4.  30 m

When a sound wave travels from one medium to another, the quantity that remains unchanged is :

1.  speed

2.  amplitude

3.  frequency

4.  wavelength

If a sound source of frequency n approaches an observer with velocity v/4 and the observer approaches the source with velocity v/5, then the apparent frequency heard will be-

1.  (5/8)n

2.  (8/5)n

3.  (7/5)n

4.  (5/7)n