Question

 A wave has a length of 30.0 cm and a velocity of 2.5 cm/s. If it has a  velocity of 3.70 cm/s when it enters a new medium, what is the  wavelength? 

Answer 1

We know velocity is directly proportional to the wavelength of the wave.

i.e $λ ∝ V$

So, $λ1/λ2 = V1/V2$

So, wavelength, $λ1 =30$ m

Velocity, $V1=2.5$ m/s

In the new medium, Velocity of the wave,$V2 = 3.7$ m/s

So, $λ1/λ2 = V1/V2$

Or, $λ2 =λ1× V2/V1$

Or, $λ2 = 30×2.5/3.7$

Or,$λ2=30×2.5/3.7$

$= 20.3$ m

when it enters a new medium, wavelength is$= 20.3$ m