What does the term 'refraction' refer to in surveying?

The term 'refraction' in surveying specifically refers to the change in angle of light as it passes through different mediums, which is option B. This phenomenon is crucial in surveying because it affects how light travels through the atmosphere, particularly when considering the interaction of light with different temperature layers or varying densities in the air.

When light passes from one medium (like air) into another (like water), or when it travels through air at different temperatures, its speed changes, causing it to bend. This bending can lead to discrepancies in the perceived location of objects when viewed through a telescope or other optical devices used in surveying. Understanding this concept helps surveyors account for potential errors in measurements caused by atmospheric conditions, ensuring greater accuracy in their work.

While the other options relate to various physical principles, they do not correctly define refraction as it pertains to surveying. Sound waves bending doesn't apply in this context, atmospheric pressure distortion is a different phenomenon, and the curvature of the earth influences distance measurements but is not related to the bending of light.