Question

A sound produces 15 crests and 15 troughs in 3 sec. When the second crest is produced, the first crest is 2 cm away from the source. Calculate the frequency, wavelength and the speed of the wave.

Answer 1

time in producing 15 trough and crests= 3 sec
distance covered by wavelength = 15λ in 3 sec

time to cover the distance of λ; T = 0.2 sec
so,
frequency = v = 1/T

as we know when the second crest is produced it is 2cm away from source, so λ= 2cm or 0.02m
so speed v= λv

Answer 2

Explanation:

time period T = 1 ÷ frequency sec.

Wavelength = 2 cm.

Number of waves produced per second = 15/3= 5.

So Frequency = 5 Hz.

Speed of the wave = frequency* wavelength

= 5 * 2 = 10 cm/sec.