NCERT Question 14 - Chapter 12 Class 9 - Sound

A sound wave travels at a speed of 339 m s –1 . If its wavelength is 1.5 cm, what is the frequency of the wave? Will it be audible?

Answer 

Speed of sound = v = 339 m/s

Wavelength = λ = 1.5cm

                          = 1.5/100 m

                          = 0.015m

Now,

Speed of sound = Wavelength × Frequency

Frequency = Speed of sound/ Wavelength

                  = v/ λ

                  = 339/0.015

                  = 339 × 1000 /15

                  = 22600 Hz

Frequency of sound is 22,600 Hz.

The audible range of human ear is 20 Hz to 20,000 Hz.

Since the frequency of sound is greater than 20,000 Hz, it won’t be audible .