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Lesson: Total Internal Reflection

In this lesson, we will learn how to define total internal reflection (TIR) by describing rays produced by light rays incident at or past the critical angle for TIR.

Sample Question Videos

02:43

Worksheet • 5 Questions • 1 Video

Q1:

The rays 𝐴 , 𝐡 , and 𝐢 are shown incident on a boundary between water and air, traveling in water. Which incident ray produces total internal reflection?

  • A ray 𝐢
  • B ray 𝐴
  • CNone of the rays produce total internal reflection.
  • D ray 𝐡

Q2:

Which of the following sets of conditions best describes total internal reflection?

  • ATotal internal reflection occurs when a light ray is completely reflected at the boundary between two media of different densities and the light ray is traveling in the higher-density medium.
  • BTotal internal reflection occurs when the angle of reflection of the reflected light ray is equal to the angle of refraction of the refracted ray.
  • CTotal internal reflection occurs when a light ray is completely reflected at the boundary between two media of different densities and the light ray is traveling in the lower density medium.
  • DTotal internal reflection occurs when a light ray is completely absorbed in an object.
  • ETotal internal reflection occurs when the reflected light ray moves along the same path as the incident light ray but in the opposite direction.

Q3:

A light ray travels along an optical fiber by total internal reflection, as shown in the diagram. What is the most correct description for what happens at point 𝑃 if light is sent into the fiber when the fiber is bent?

  • ASome of the light is transmitted out of the fiber at 𝑃 because the angle of incidence there is less than the critical angle.
  • BThe light totally internally reflects at 𝑃 because the angle of incidence there is less than the critical angle.
  • CSome of the light is transmitted out of the fiber at 𝑃 because the angle of incidence there is greater than the critical angle.
  • DThe light totally internally reflects at 𝑃 because the angle of incidence there is greater than the critical angle.
  • ESome of the light is refracted along the fiber surface at 𝑃 because the angle of incidence there is equal to the critical angle.
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