An observer moves towards a stationary source of sound with a speed (1/5)t h of the speed of sound. The wavelength and frequency of the source emitted are λ and f respectively. The apparent frequency and wavelength recorded by the observer are respectively

Question

An observer moves towards a stationary source of sound with a speed (1/5)t h of the speed of sound. The wavelength and frequency of the source emitted are λ and f respectively. The apparent frequency and wavelength recorded by the observer are respectively (A) 1.2f,1.2λ  (B) 1.2f,λ  (C) f,1.2λ  (D) 0.8f,0.8λ

Tardigrade Admin · Accepted Answer

Apparent frequency, f'=((v + v0/v))f ⇒ f'=((v + (1 / 5) v/v))f=1.2f Wavelength does not change by motion of observer.

Q. An observer moves towards a stationary source of sound with a speed $\frac{1}{5}^{t h}$ of the speed of sound. The wavelength and frequency of the source emitted are $λ$ and $f$ respectively. The apparent frequency and wavelength recorded by the observer are respectively

$1.2 f, 1.2 λ$

$1.2 f, λ$

$f, 1.2 λ$

$0.8 f, 0.8 λ$

Apparent frequency, $f^{^{'}} = (\frac{v + v _{0}}{v}) f$
$\Rightarrow f^{^{'}} = (\frac{v + ( 1/5 ) v}{v}) f = 1.2 f$
Wavelength does not change by motion of observer.

Q. An observer moves towards a stationary source of sound with a speed 51​th of the speed of sound. The wavelength and frequency of the source emitted are λ and f respectively. The apparent frequency and wavelength recorded by the observer are respectively

1.2f,1.2λ

1.2f,λ

f,1.2λ

0.8f,0.8λ