Two wave trains, with intensities I and 2I respectively arrive and superpose at a point P in opposite phases. The amplitude of the superposed wave at P at that instant will be proportional to,

1. $\sqrt{3I}$

2. $\sqrt{I}$

3. $\sqrt{\left(3-2\sqrt{2}\right)I}$

4. $\left(\sqrt{2}+1\right)\sqrt{I}$

Assertion: In a stationary wave, there is no transfer to energy.

Reason: There is no outward motion of the disturbance from one particle to adjoining particle in a stationary wave.

The speed of sound in a gas is \(v\) and the r.m.s. velocity of the gas molecules is \(c\). The ratio of \(v\) to \(c\) is:
1. \(\frac{3}{\gamma}\)
2. \(\frac{\gamma}{3}\)
3. \(\sqrt{\frac{3}{\gamma}}\)
4. \(\sqrt{\frac{\gamma}{3}}\)

Two pulses is a stretch string whose centers are initially 8 cm apart are moving towards each other as shown in the figure. The speed of each pulse is 2 cm/s . After 2 seconds, the total energy of the pulses will be:

1.  zero

2.  Purely kinetic

3.  Purely potential

4.  Partly kinetic and partly potential 

The graph between wave number ($\overline{\mathrm{v}}$) and angular frequency ($\mathrm{\omega }$) is

Three sound waves of equal amplitudes have frequencies of \((n-1),~n,\) and \((n+1).\) They superimpose to give beats. The number of beats produced per second will be:

The fundamental frequency in an open organ pipe is equal to the third harmonic of a closed organ pipe. If the length of the closed organ pipe is \(20~\text{cm}\), the length of the open organ pipe is:
1. \(13.2~\text{cm}\)
2. \(8~\text{cm}\)
3. \(12.5~\text{cm}\)
4. \(16~\text{cm}\)

If the intensity is increased by a factor of 20; then how many decibels in the sound level increased?

1. 18

2. 13

3. 9

4. 7

A source of sound S emitting waves of frequency 100 Hz and an observer O are located at some distance from each other. The source is moving with a speed of 19.4 ms^-1 at an angle of ${60}^0$ with the source-observer line as shown in the figure. The observer is at rest. The apparent frequency observed by the observer (velocity of sound in air 330 ms^-1), is: 
              

1. 100 Hz

2. 103 Hz

3. 106 Hz

4. 97 Hz