Refraction

The act of refracting, or the state of being refracted.

The change in the direction of ray of light, heat, or the like, when it enters obliquely a medium of a different density from that through which it has previously moved.

The change in the direction of a ray of light, and, consequently, in the apparent position of a heavenly body from which it emanates, arising from its passage through the earth's atmosphere; -- hence distinguished as atmospheric refraction, or astronomical refraction.

The correction which is to be deducted from the apparent altitude of a heavenly body on account of atmospheric refraction, in order to obtain the true altitude.

the change in direction of a propagating wave (light or sound) when passing from one medium to another

the amount by which a propagating wave is bent