Question

The source of sounds produces 20 compressions and 20 rarefactions in 0.2 seconds. The distance between one compression and rarefaction is 50 cm. Find the wavelength ,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