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Home Minds On Refraction and Lenses Mission RL2 Light Speed and Refraction Help Help 3

Mission RL2 Light Speed and Refraction

The Question

Suppose a beam of light is passing at an angle from a medium in which it moves fast into a medium in which it is moving slower. For such a case, the angle of incidence is ____ the angle of refraction.

Physics Rules

The Direction of Bending:
Refraction is the bending of the path of light as it passes across the boundary between two media. The direction of bending is dependent upon the relative speed at which light moves within the two media. The rules are:
  • When light passes from a medium in which it travels faster into a medium in which it travels slower, the light ray will refract towards the normal line.
  • When light passes from a medium in which it travels slower into a medium in which it travels faster, the light ray will refract away from the normal line.

Think About It

The diagram provides two examples of light bending - in one case towards the normal and in the other case away from the normal. The two diagrams are only intended to assist you in thinking about the direction of bending and how it relates to the angles of incidence and refraction. It is recommended that you first identify which of the two diagrams is representative of the situation described in the question (see Know the Law section). Then use the definitions of the angle of incidence and refraction to answer the question (see Dictionary section).

Define Help

Definition of Angle of Incidence:
The angle of incidence is the angle made between the ray of light approaching a surface (incident ray) and the normal line drawn to the surface at the location where the ray contacts the surface.
 

Definition of Angle of Refraction:
The angle of refraction is the angle made between the ray of light entering the new medium (refracted ray) and the normal line drawn to the surface at the location where the ray enters into the new medium.

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