Why does the wavelength of light change when passing from one medium to another and

Why does the wavelength of light change when passing from one medium to another and does not change the frequency?

When light passes from one medium to another, the speed of propagation of light V and the wavelength λ change, the frequency of the wave v does not change.
Light is electromagnetic radiation.
According to the definition of the wavelength λ is the distance that the wave travels in a time equal to the oscillation period. This distance depends on the properties of the medium in which the light travels. The optically denser the medium, the more difficult it is for light to travel a distance in the same time.
In optically denser media, the won length will be shorter than in less optically dense media.
And the frequency of oscillations is a characteristic of the radiation itself, how the lines of force of the electric and magnetic fields change.