What is an example of total internal reflection at work?

A.
A ray of light has the same intensity both entering and exiting a fiber optic cable.
B.
A ray of light entering a glass cube gets refracted.
C.
A ray of light in air hits a shiny surface and bounces off.
D.
A ray of light entering a ruby gets refracted.

[tex]\leadsto[/tex] Total internal reflection occurs when a ray of light is traveling through a medium and, when that medium changes, it does not refract into the second medium but instead it reflects back into the first medium.

By Snell's law, we know that

[tex]\longrightarrow \sf{n_1 sin \emptyset_1 = n_2 sin \emptyset_2}[/tex]

If this happens, then [tex]\sf{n_2 \angle n_1}[/tex], and the ray does not lose intensity due to refraction.

[tex]\huge\underline{\underline{\boxed{\mathbb{ANSWER:}}}}[/tex]

[tex]\large \bm{ A.}[/tex] A ray of light has the same intensity both entering and exiting a fiber optic cable.