When a wave refracts, its wavelength and frequency do not change. However, the wave's velocity and direction do change.
The velocity of a wave is the distance that the wave travels in a given amount of time. The frequency of a wave is the number of waves that pass a given point in a given amount of time.
The wavelength of a wave is the distance between two consecutive peaks or troughs of the wave. The frequency of a wave is inversely proportional to its wavelength. This means that as the wavelength of a wave increases, its frequency decreases.
When a wave refracts, its velocity changes because the wave is traveling through a different medium. The wave's frequency does not change because the number of waves that pass a given point in a given amount of time does not change.
The direction of a wave changes when it refracts because the wave is traveling at a different angle to the surface of the medium. The wave's wavelength and frequency do not change because these properties of a wave are independent of the direction of the wave.
