Question

Suppose a ray of light traveling in a material with an index of refraction na reaches an interface with a material having an index of refraction nb. Which of the following statements must be true for total internal reflection to occur?Check all that apply.a. The angle of incidence must be less than the critical angle.b. na = nbc. na > nbd. The angle of incidence must be greater than the critical angle.e. The angle of incidence must be equal to the critical angle.

Answer 1

Answer: Option (b) is the correct answer.

Explanation:

It is known that when a ray of light tends to travel from a denser to rarer medium then there occurs total internal reflection.

For a denser medium the refractive index is greater than that of a rarer medium. This means that for the given situation refractive index of medium $n_{a}$ is greater than medium $n_{b}$.

this also means that incident angle must be greater than the critical angle of the medium.

Thus, we can conclude that the statement $n_{a}$ > $n_{b}$ must be true for total internal reflection to occur.