Question

A source of sound produced 20 compression and 20 rarefaction in 0.2 seconds. distance b/w compression and rarefaction = 50 cm.
Find wavelength,frequency and time period?

Answer 1

wavelength = distance between 2 consecutive compression or rarefaction
= 2*50
= 100 cm = 1m

20 waves are produced in 0.2 secs
hence frequency = 20/0.2= 100 Hz

time period = 1/f = 0.01 sec

Answer 2

Wavelength = 2 × Distance between compression and rarefaction
……………[see image attached]
= 2 × 50 cm
= 100 cm
Wavelength of sound is 100 cm

It makes 20 compressions and 20 rarefactions in 0.2 seconds.
Time period: Time taken for one compression and one rarefaction.
So, Time period = 0.2 s / 20 = 0.01 second

Frequency = 1 / Time period
= 1 / 0.01 s
= 100 Hz
Frequency of sound is 100 Hz