What does the term 'refraction' generally refer to in optics?

The term 'refraction' in optics specifically refers to the bending of light as it passes from one medium to another with a different density. This bending occurs due to changes in the speed of light as it moves through different materials, such as air to water or glass.

When light travels through different media, it changes speed, leading to a change in direction. This phenomenon is crucial in understanding various optical devices, such as glasses, cameras, and microscopes, where precise control of light is necessary for focusing and image clarity.

Refraction is fundamental in creating lenses that manipulate light to provide magnification or correction for vision. The principles of refraction are also foundational for understanding how rainbows form and why objects appear distorted when viewed through water. The other options, while related to light, describe different interactions: absorption involves light being taken in by an object, emission relates to light being produced by sources, and reflection refers to light bouncing off surfaces—none of which capture the essence of refraction.