Question

(a) Explain the terms 'crests' and troughs' of a wave? What type of waves consist of crests and troughs?
(b) The flash of a gun is seen by a man 3 seconds before the sound is heard. Calculate the distance of the gun from the man (Speed of sound in air is 332 m/s).

Answer 1

(a) A transverse wave consists of crests and troughs.
The elevation or hump in a transverse wave is called crest. It is that part of the transverse wave in which all the medium particles are above the line of zero disturbance of the medium.
The depression or hollow in a transverse wave is called trough. It is that part of the transverse wave in which all the medium particles are below the line of zero disturbance of medium.

(b)We have to find the distance to which the sound will reach in a given time.
Given: Velocity of sound ν = 332 m/s
Time t = 3 s
So,
Distance = Speed × Time
Therefore, distance covered is
= 332 × 3 m
= 996 m