Question

Sound waves of wavelength $\lambda$travelling in a medium with a speed of v m $s^{- 1}$ enter into another medium where its speed is 2v m $s^{- 1}$ wavelength of sound waves in the second medium is.

• A. $\lambda$
• B. $\frac{\lambda}{2}$
• C. $2\lambda$
• D. $4\lambda$

Answer 1

Answer: (C)

$2\lambda$

Answer 2

Wavelength of sound waves in the second Medium

$\lambda = \frac{v}{\upsilon}$ …. (i)

Wavelength of sound waves in the seconds medium

$\lambda' = \frac{2v}{\upsilon'}$ ….. (ii)

As the frequency of the wave remains unchanged with the change in medium

$\therefore\upsilon = \upsilon'$ ...... (iii)

Divide (ii) by (i), we get

$\frac{\lambda'}{\lambda} = 2$ [Using (iii)]

Or $\lambda' = 2\lambda$