Waves of Sound

Q.

A stone is dropped into a lake from a tower 500 metre high. Taking the speed of sound as 330 m/s, the sound of the splash will be heard by the man approximately after

1. 11.5 seconds

2. 21 seconds

3. 10 seconds

4. 14 seconds

Q. A sound wave of frequency 100 Hz is travelling in air. The speed of sound in air is 350 m s${}^{-1}$. By how much is the phase changed at a given point in 2.5 ms?

1. $\pi$

2. $\frac{3\pi }{5}$

3. $\frac{\pi }{2}$

4. $0.2\pi$

Q.

If in a medium wave's wavelength is decreased, what will happen to its frequency?

1. Increase

2. Decrease

3. Frequency Doesn't depend on wavelength

4. Data insufficient need density too