Mammoth Memory

Angle of incidence and angle of refraction

Angle of incidence is the angle between a ray incident on a surface and the normal line.

Angle of incidence between a light ray and the normal line.

To remember a "Ray Incident" use the mnemonic.

Ray incident mnemonic picture.

Remember the "incident" started here. This will help you remember that the ray of light has to start when an incident occurs.

The angle of refraction is just the opposite of the angle of incidence, that is:

The angle of refraction is the angle between the refracted ray and the normal line.

The angle of incidence is the angle between the ray of light and the normal line approaching the boundary and the angle of refraction is the angle between the ray of light and the normal line after the boundary.

If light travelling through air has an angle of incidence of 40° then:

Angle of incidence of air 40° - Water angle of refraction 29°

Angle of incidence of air 40° - Glass angle of refraction 25°

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