What happens when a light ray is incident normally to the interface of two media?

When a light ray is incident normally (or perpendicularly) to the interface of two media, it continues to travel in a straight line into the second medium without any deviation. This is because the angle of incidence is 0 degrees, and according to Snell's Law (which states that the ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant), when the angle of incidence is 0, the angle of refraction is also 0. Therefore, the light does not change direction. However, the speed and wavelength of the light may change as it enters the second medium, depending on the refractive indices of the two media. If the second medium has a higher refractive index, the light will slow down and the wavelength will decrease. If the second medium has a lower refractive index, the light will speed up and the wavelength will increase.