The angle of incidence (qi) equals the angle of reflection (qr.)

(Student Friendly: If a ray of light hits a barrier at an angle, then the ray will bounce off the barrier with the exact same angle.)

qi qr

Light will bend when it changes mediums because its velocity is changed once it leaves a vacuum.

When the velocity is slowed the light is bent

toward the normal.

When the velocity

is increased it is

bent away from the

normal.

The index of refraction is the value a substance has because of the way it bends light as it travels through the substance.

The index of refraction (ni) of the incident medium times the sine of the angle of incidence equals the index of refraction (nr) from the refracted medium times the sine of the angle of refraction.

ni sine qi = nr sine qr

This is easy to use. You are either finding an angle or an index of refraction.

A ray of light from air is incident on plexiglassat an angle of 29o. It is bent at an angle of 35o. What is the refracted index value of plexiglass?

Use index for air of 1.003.

ni = 1.003 nr = ? qi = 29o qr = 35o

1.003 x sine 29 = nr sine 35

.4863/.5736 nr = .85