Question

A source produces 60 rarefactions and 60 compressions in 0.6 s. Distance between a compression and the next (consecutive) rarefaction is 150 cm. Find the frequency of the wave :

• A. 500 Hz.
• B. 0.02
• C. 0.01 Hz
• D. 100 Hz

Answer 1

The correct option is D 100 Hz

Frequency of wave is defined as the number of waves produced in 1 second. A longitudinal wave is formed by one compression and one rarefaction, we have 60 compressions and 60 rarefactions in $0.6s$ i.e. 60 waves produced in 0.6s,

In $0.6s$ the number of wave produced $=60$

In $1s$ the number of wave produced $=\frac{60}{0.6}=100Hz$

Therefore , frequency $f=100Hz$

Here, the distance given between a compression and the next (consecutive) rarefaction is of no use. It is wavelength. We need only number of waves and time to calculate frequency.