What is the term for lights changing direction as they pass from one medium to another?

The term that describes lights changing direction as they pass from one medium to another is refraction. Refraction occurs due to the change in speed of light as it enters a different medium, which has a different density. For example, when light moves from air into water, it slows down and bends at the interface between the two mediums. This bending effect is what allows us to perceive objects differently when they are submerged in water compared to when they are in air.

In contrast, reflection refers to the bouncing back of light when it hits a surface, maintaining its original direction in the opposite way. Diffraction involves the bending of light waves around obstacles or through openings, causing them to spread out, rather than changing direction upon entering a new medium. Absorption occurs when light is taken up by a material, converting its energy into other forms, which usually results in a decrease in the intensity of the light rather than a change in its direction.

Understanding refraction is essential in opticianry, as it plays a crucial role in the function of lenses, which are used to correct vision by bending light to focus it correctly onto the retina.