What is the process called when light changes direction as it passes from one transparent medium to another?

The process when light changes direction as it passes from one transparent medium to another is known as refraction. Refraction occurs because light travels at different speeds in different materials; when it enters a medium where its speed is different, it bends. This bending of light can be observed when, for example, a straw appears to be bent when placed in a glass of water. The degree to which the light bends depends on the indices of refraction of the two media.

This phenomenon is integral to various applications in optics, such as the design of glasses and lenses, where understanding how light behaves at the interface between air and glass allows for correcting vision or focusing images effectively. Refraction is fundamentally linked to the wave nature of light and is governed by Snell's Law, which mathematically defines the relationship between the angles and the refractive indices of the two media.

The other options like reflection, diffraction, and absorption refer to different phenomena: reflection involves light bouncing off a surface, diffraction relates to the bending of light around obstacles or through openings, and absorption is the process where light is taken up by a material and converted to other forms of energy. Each of these processes describes unique interactions of light and does not involve the bending that occurs specifically in refraction