Reflection and Refraction: Answers

What is the law of reflection?

The law of reflection states that the angle of incidence is equal to the angle of reflection. This means that if a light ray hits a mirror at a certain angle, it will bounce off (be reflected) from the surface of the mirror at exactly the same angle.

Light moves along an optical fibre by total internal reflection.

• Sketch a diagram to show the path of a light ray as it enters and passes through the optical fibre.

• State two conditions required for total internal reflection to happen.

  For total internal reflection to happen, the wave must travel from a more dense material to a less dense one and the angle of incidence must be greater than the critical angle.

What is refraction?

Refraction is the change in direction of a wave when it passes from one material to another (at a boundary).

Sketch a ray diagram to show the refraction of a light ray as it passes from air to water.

State the equation linking refractive index, angle of incidence and angle of refraction.

Refractive index (n) = sin of angle of incidence (sin i) / sin of angle of reflection (sin r).