Question

When a wave travels from air into water and the wavelength increased twice then find: The wave speed will

Answer 1

The frequency of wave does not change as it goes from one medium to another. The wave speed is in air is given as follows:

$$v_1 = \lambda_1\nu$$

where $\lambda_1$ is the wavelength in air and $\nu$ is the frequency.

In water $\lambda_2 = 2\lambda_1$ and the speed is:

$$v_2 = \lambda_2\nu=2\lambda_1\nu = 2v_1$$

Answer. The speed increased twice.