The document discusses the laws of reflection and refraction of light. It states that the angle of incidence equals the angle of reflection, and that light bends when changing mediums due to changes in velocity. The index of refraction is a value that indicates how much a substance bends light. Snell's law states that the index of refraction of the incident medium times the sine of the angle of incidence equals the index of refraction of the refracted medium times the sine of the angle of refraction. An example calculation is shown to find the index of refraction of plexiglass using measurements and air's known index of refraction.

2.  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

3.  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.

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

6.  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.

7.  A ray of light from air is incident on plexiglass
at 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