# Worksheet: Total Internal Reflection

In this worksheet, we will practice defining total internal reflection (TIR) by describing rays produced by light rays incident at or past the critical angle for TIR.

Q1:

The rays , , and are shown incident on a boundary between water and air, traveling in water. Which incident ray produces total internal reflection? • ARay
• BRay
• CRay
• DNone of the rays

Q2:

Which of the following definitions best describes the critical angle for total internal reflection?

• AThe critical angle is the angle at which the refracted ray travels along the boundary from which the incident ray is reflected.
• BThe critical angle is the angle of incidence plus the angle of refraction.
• CThe critical angle is the angle of incidence minus the angle of refraction.
• DThe critical angle is the angle of refraction minus the angle of incidence.
• EThe critical angle is the angle at which all incident light at a boundary is reflected.

Q3:

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

• ATotal internal reflection occurs when a light ray is completely absorbed in an object.
• BTotal 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.
• CTotal internal reflection occurs when the reflected light ray moves along the same path as the incident light ray but in the opposite direction.
• DTotal internal reflection occurs when the angle of reflection of the reflected light ray is equal to the angle of refraction of the refracted ray.
• ETotal 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.

Q4:

A light ray travels along an optical fiber by total internal reflection, as shown in the diagram. The light reflects from the internal surface of the fiber at an angle very slightly greater than the critical angle. What is the most correct description for what happens at point if light is sent into the fiber when the fiber is bent? • ASome of the light is transmitted out of the fiber at because the angle of incidence there is greater than the critical angle.
• BSome of the light is refracted along the fiber surface at because the angle of incidence there is equal to the critical angle.
• CSome of the light is transmitted out of the fiber at because the angle of incidence there is less than the critical angle.
• DThe light totally internally reflects at because the angle of incidence there is greater than the critical angle.
• EThe light totally internally reflects at because the angle of incidence there is less than the critical angle.

Q5:

Which of the following most correctly describes what happens if a light ray traveling in water contacts a boundary between air and water at an angle greater than the critical angle for a water–air interface?

• AThe light completely reflects from the air back into the water.
• BThe light propagates along the boundary between air and water.
• CSome light is transmitted from the water into the air and some light reflects from the air back into the water.
• DThe light is completely transmitted from the water into the air.

Q6:

The diagram shows light rays in water being totally internally reflected at a boundary with air. The diagram also shows a light ray in air incident on the same boundary and at the same angle of incidence. Which of the paths , , and would light incident on water from air follow? • ARay
• BRay and Ray
• CRay
• DRay
• ERay and Ray

Q7:

The diagram shows two different light rays propagating through an optical fiber cable. Two angles are shown, one in green and one in blue. Which of the following statements about these angles is correct? • AThe blue angle and the green angle are both larger than the critical angle.
• BThe blue angle is smaller than the critical angle, but the green angle is larger than the critical angle.
• CThe blue angle is larger than the critical angle, but the green angle is smaller than the critical angle.
• DThe blue angle and the green angle are both smaller than the critical angle.

Q8:

The diagram shows two different light rays propagating through an optical fiber cable. Two angles are shown, one in green and one in blue. Which of the following statements about these angles is correct? • AThe blue angle is smaller than the critical angle, but the green angle is larger than the critical angle.
• BThe blue angle and the green angle are both smaller than the critical angle.
• CThe blue angle and the green angle are both larger than the critical angle.
• DThe blue angle is larger than the critical angle, but the green angle is smaller than the critical angle.

Q9:

The diagram shows two different light rays propagating through an optical fiber cable. Two angles are shown, one in green and one in blue. Which of the following statements about these angles is correct? • AThe blue angle and the green angle are both larger than the critical angle.
• BThe blue angle is larger than the critical angle, but the green angle is smaller than the critical angle.
• CThe blue angle and the green angle are both smaller than the critical angle.
• DThe blue angle is smaller than the critical angle, but the green angle is larger than the critical angle.

Q10:

The diagram shows two different light rays propagating through an optical fiber cable. Two angles are shown, one in green and one in blue. Which of the following statements about these angles is correct? • AThe blue angle and the green angle are both smaller than the critical angle.
• BThe blue angle is larger than the critical angle, but the green angle is smaller than the critical angle.
• CThe blue angle is smaller than the critical angle, but the green angle is larger than the critical angle.
• DThe blue angle and the green angle are both larger than the critical angle.