1. Geometric Optics
Sarah & Emma

2. i. Law of Reflection
• Angle of incidence = angle of reflection
• Incident ray, reflected ray and normal line all
lie on same plane

3. Mirror
Reflected ray
Normal line Incident ray
Object
Angles of incidence
Angles of refraction
Source: ppt

4. Specular vs. Diffuse reflection
• Specular reflection – reflection off smooth
surface (i.e. mirror)
• Diffuse reflection – reflection off rough
surfaces (i.e. asphalt)

5. • A rough surface diffuses light because every
individual light ray hits a point of the surface
that is oriented at a different angle. This
means they will reflect at all different angles.
• Source: http://www.physicsclassroom.com/class/refln/U13L1d.cfm

6. ii. Refraction
• Bending of light – light bends when it passes
from one medium to another
• The boundaries where refraction takes place
are called interfaces
Glass
interfaces
Light

7. nglass=speed of light in vacuum/ speed of light in glass
≈speed of light in air/speed of light in glass
• These two “index of refraction”s are the same
to 3 sig figs

8. Snell’s Law
• For a given substance, the ratio sin(angle of
incidence)/sin(angle of refraction) is a
constant
Angle of incidence (θair)
Angle of refraction (θglass)
Normal line
Light

9. Angle of incidence (θair)
Angle of refraction (θglass)
Normal line
Light
nglass = sinθvacuum/sinθglass = vvacuum/vglass
≈ sinθair/sinθglass = vair/vglass

10. • If we add a substance other than air (glass &
water instead of air & water)…
θglass Glass
Water
θwater
• nXsinθX = nysinθy= nzsinθz = … as long as the
interfaces are parallel

11. • The denser the substance, the greater the
index of refraction
• As light goes from less dense to denser, it
bends toward the normal (angle of incidence >
angle of refraction)
• As light goes from denser to less dense, it
bends away from normal (angle of incidence <
angle of refraction)

12. iii. Prism
• Dispersion – separation of visible light into its
different colors
• Angle of deviation –overall refraction caused
by passage of light ray through prism

13. Dispersion
• Different colored lights have different
frequencies
• Therefore they travel through material w/
different speeds
• This leads to different angles of refraction and
the dispersion of light

14. Deviation
• Angle of deviation – angle b/w incident ray
and refracted ray that leaves prism
θblue θred