When light travels from one medium to another, such as from air to glass, its velocity and wavelength change due to the change in the optical properties of the medium. However, the frequency of the light remains the same.
The frequency of light refers to the number of complete oscillations of the electric and magnetic fields that make up the light wave per unit of time. It is a fundamental characteristic of light and determines its color or energy. The frequency of a light wave is directly related to the energy carried by the photons that make up the wave.
When light passes through different media, the speed at which it propagates changes due to interactions with the atoms or molecules of the medium. In a denser medium like glass, the speed of light is typically lower than in a less dense medium like air.
According to the wave equation, the speed of light (v) is equal to the product of its frequency (f) and wavelength (λ):
v = f * λ
Since the speed of light changes when it enters a different medium, either the frequency or the wavelength (or both) must also change to maintain this equation.
When light enters a medium with a different refractive index, such as glass, its velocity decreases. To keep the equation balanced, the wavelength of light decreases proportionally to the decrease in velocity. This is why light appears to bend or refract when passing through a medium with a different refractive index.
However, the frequency of light remains the same because it is an intrinsic property of the light wave itself and is not affected by the medium it passes through. The frequency determines the color or energy of the light, and it remains constant regardless of the medium.