Refraction of light — Describe

What is the difference between internal reflection and total internal reflection, and what are some examples?

When light in a denser medium meets a boundary with a less dense medium, part of it is reflected back into the denser medium at all angles of incidence — this is (partial) internal reflection. Total internal reflection (TIR) occurs only when the angle of incidence exceeds the critical angle, so all the light is reflected and none is refracted out. This can be shown experimentally with a semicircular glass block, where increasing the angle of incidence inside the glass past the critical angle causes the refracted ray to vanish, leaving only a reflected ray. Everyday examples include the sparkle of a cut diamond and the use of prisms in periscopes, plus transmission of light along optical fibres.