1. Refraction: This is the bending of light as it passes from one medium to another. This happens because the speed of light changes as it enters the new medium. The amount of bending depends on the refractive index of the two media.

* Higher Refractive Index: Light slows down, and the light ray bends *towards* the normal (an imaginary line perpendicular to the surface of the medium).

* Lower Refractive Index: Light speeds up, and the light ray bends *away* from the normal.

2. Change in Speed: Light travels at different speeds in different mediums. In a vacuum, it travels at its maximum speed, approximately 299,792,458 meters per second. However, light slows down when it enters a medium like water, glass, or air. The speed of light in a medium is determined by the refractive index of the medium.

3. Change in Wavelength: The wavelength of light also changes as it enters a new medium. This is because the frequency of the light remains constant, but the speed changes. Since the relationship between speed, frequency, and wavelength is:

* Speed = Frequency x Wavelength

If the speed decreases, the wavelength must also decrease to maintain the same frequency.

4. Partial Reflection: Some of the light may be reflected back at the boundary between the two media. The amount of reflected light depends on the difference in refractive indices between the two media.

5. Scattering: Light may be scattered in different directions as it interacts with the particles within the new medium. This is particularly noticeable in media that are not transparent, such as fog or clouds.

In Summary:

When light enters a new medium, it slows down, changes direction (refracts), and its wavelength shortens. Some of the light may be reflected back, and the light may also be scattered.