Question

A body sends waves 100 mm long through medium A and 0.25 m long in medium B. If the velocity of waves in medium A is 80 cm s–1. The velocity of waves in medium B is

• A. 1 m s–1
• B. 2 m s–1
• C. 3 m s–1
• D. 4 m s–1

Answer 1

Answer: (B)

2 m s–1

Answer 2

Here, $\lambda_{A} = 100mm = 0.10m$

$\lambda_{B} = 0.25m$

$v_{A} = 80cms^{- 1} = 0.80ms^{- 1}$

As the frequency of the wave remains same in the two media.

$\therefore\upsilon = \frac{v_{A}}{\lambda_{B}} = \frac{v_{B}}{\lambda_{B}}$

$\therefore v_{B} = \frac{\lambda_{B}}{\lambda_{A}} \times v_{A} = \frac{0.25}{0.10} \times 0.80$

$\Rightarrow V_{B} = 2ms^{- 1}$