Question

When a sound wave passes from air into water, do you expect the frequency or wavelength to change?

Short answer

When the wave is going from air to water, the wavelength changes due to wave speed, the speed of the sound wave is four times in water than in air. Therefore, the wavelength in water is four times longer than in air.

Step-by-step solution

Write the concept when sound is travelling from one medium to another

If the wave's frequency is changing, then the two mediums cannot be in contact. When the frequency of vibration is different for two mediums, then the particle of mediums cannot stay in contact. But in order to transmit a wave, the particles must be in contact. So, the frequency will not change.

Write the behaviour of sound wave when it is going from air to water 

When the wave is going from air to water, the speed of the wave will change, but the frequency will remain the same, but the wavelength will change. The speed of the sound wave is four times in water than in air. Therefore, the wavelength in water is four times longer than in air.