Question

21
A sound wave of wavelength 80 cm in glass enters into the air. If the velocities
of sound in glass and air 5600 m/s and 340 m/s, calculate the wavelength of
sound in air.​

Answer 1

Explanation:

Given,

Velocity V=340m/s

Wavelength λ=2cm=0.02m

Frequency f=?

We have,

V=F.λ

⇒340=F×0.02

F=

0.02

340

=17,000Hz

As the audible range is in between 20Hz and 20,000Hz this sound wave is at audible range.

Answer 2

Answer:

A sound wave of wavelength 80 cm in glass enters into the air. If the velocities  of sound in glass and air 5600 m/s and 340 m/s, the wavelength of  sound in the air will be $0.0486\ m$

Explanation:

• The expression for velocity (v) of a wave in a medium  is given by the expression,

        $v=f \lambda$      

       that is,

       $f = \frac{v}{\lambda}$      ...(1)

       or

       $\lambda= \frac{v}{f}$      ...(2)

      where f is the frequency and $\lambda$ is the wavelength of the wave.

• Since the source of the wave is the same, the frequency of waves produced in water and glass will have the same value.

       

In the question, it is given that,

the wavelength of sound in glass      =   $80\ cm = 0.80m$

the speed of sound in glass               =    $5600\ m/s$

Using equation(1),

frequency of sound,

$f = \frac{5600}{0.80} = 7000 Hz$

Given,

The velocity of sound in air  =    $340\ m/s$

Using equation(2),

• the wavelength of the sound wave in air     =    $\frac{340}{7000} = 0.0486\ m$