Question

A source of sound produces 20 compressions and 20 rarefactions in 0.2seconds . The distace between a compression and a rerefaction is 50cm . Find the wave length, frequency and time period of the wave.

Answer 1

Wavelength is total path length between two rarefractions or compression
So, Wavelength = 50 × 2 = 100 cm
And, Frequency = 20/0.2
                           = 100 Hz
We know,
Time period = 1/f
                    = 1/100
                    = 0.01 second 

Answer 2

Time period = 0.2 sec
Distance between a compression and rarefaction = 50 cm = 0.5 metres

Wavelength = 2 x Distance between a compression and rarefaction
= 2 x 0.5 = 1 meter

Frequency = No : of waves formed in 1 sec

20 waves are formed in 0.2 sec

No : of waves formed in 1 sec = 20 / 0.2 = 100 Hz

Frequency = 100 Hz

Frequency = 1 / Time period
Hence , time period = 1 / Frequency
= 1 / 100
= 0.01 sec