Question

(a) Explain the terms 'crests' and 'troughs of a wave? What type of waves consist of crests and troughs?
â(b) The flash of a gun is seen by 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

Explanation:

(a) The crests and troughts are present in the transverse. The hump or elevation in a transverse wave is known as crest.  

• Crest is the transverse wave’s part in which the medium particles are present on top of the zero-disturbance line of the medium.
• The hollow or the depression in a transverse wave is known as the trough. It is the transverse wave’s part in which the medium particles are present below the medium’s zero disturbance line.  

(b) The light’s speed is $3 \times 10^{8}.$ When the gun is fired, the flash is seen. Thus, the speed’s formula is equal to distance/time.  

• In air, the sound’s speed is 332 m/s and the time is 3 seconds.
• When these values are substituted, then we get: $(D)=332 \mathrm{m} / \mathrm{s} \times 3 \mathrm{s}$

        So,$D=996 m$.