Sound waves of wavelength λ travelling in a medium with a speed of v m/s enter into another medium where its speed is 2v m/s. The wavelength of sound waves in the second medium is:

1. λ

2. λ2

3. 2λ

4. 4λ

(3) Hint: The frequency of the wave remains the same.
Step 1: Find the wavelength of the wave in the second medium.
Let the frequency in the first medium is ν and in the second medium is ν'.
Frequency remains the same in both the medium.
So,                                                     ν=ν'vλ=v'λ'
And v and v' are speeds in the first and second medium respectively.
So,                                                  λ'=2vvλ=2λ