Revisiting Waves

Q. Consider a pulse created on the horizontal string highlighted. The net force applied by particles $A$ and $C$ on $B$ will be in

1. upward direction
2. downward direction
3. left direction
4. right direction

Q. A microphone of cross-sectional area 0.80 $c{m}^2$ is placed in front of a small speaker emitting 3.0 W of sound output. If the distance between the microphone and the speaker is 2.0 m, how much energy falls on the microphone in 5.0 s?

1. $12\mu J$

2. $80\mu J$

3. $24\mu J$

4. $30\mu J$

Q. A source of sound of frequency $50H_Z$ is producing longitudinal waves in air. The amplitude of vibrations of air particles is 5mm and the speed of the wave is $330m{s}^{-1}$. Write the equation of the wave.

1. $y=5\times {10}^{-3}sin[100\pi t-\frac{100\pi x}{33}]$
2. $y=0.05sin[220\pi t-\frac{\pi x}{3}]$
3. $y=0.05sin[110\pi t-\frac{2\pi x}{3}]$
4. $y=0.05sin[110\pi t-\frac{\pi x}{3}]$

Q.

A wave of wavelength 0.60 cm is produced in air and it travels at a speed of 300 m s${}^{-1}$. Will it be audible?

1. Yes

2. No

3. Data insufficient

Q. The sound from a very high burst of fireworks takes 5 s to arrive at the observer. The burst occurs 1662 m above the observer and travels vertically through two stratifier layers of air, the top one of thickness
$d_1$ at $0^{\circ }C$ and the bottom one of thickness $d_2$ at ${20}^{\circ }C$. Then (assume velocity of sound at $0^{\circ }C$ is 330 m/s)

1. $d_1=342m$
2. $d_2=1320m$
3. $d_1=1485m$
4. $d_2=342m$