LIGHT: OBSERVATIONS

1
LIGHT OBSERVATIONS

• Light propagates in straight lines
• from a source.

Makes triangulation, surveying, star location,
etc. possible.
2
REFLECTION
normal
qr
qi
air
qi qr
glass
Incident ray, reflected ray, normal, lie in a
plane.
3
REFRACTION
Light Beam
qi
Air
Water
qr
qi gt qr
4
VARYING qi FOR AIR/WATER
qr
qi
7.5 22.1 40.6 47.8
10 30 60 80
5
INDEX OF REFRACTION
For light propagating between air and another
transparent material, n sinqi/sinqr is the
index of refraction of the material
The value of n depends on the material water n
1.33 glass n 1.5 diamond n 2.4
6
TOTAL REFLECTION
glass or plastic
7
LIGHT PIPES
8
INTERSECTING BEAMS

• When two light beams intersect, they do not
  interact with each other at all.

9
COLOR
10
INTERPRETATION
The index of refraction varies with color.
For Glass Red 1.514 Green
1.520 Violet 1.529
11
POLARIZATION
I(q) I0cos2(q)
12
THE RAINBOW
420 maximum return angle
13
BACKSCATTERING CONE
no backscattering
From sun
backscattering
14
CORNER REFLECTOR
q
15
CRUDE LENS
16
CRUDE LENS
17
AIR BUBBLE IN WATER
18
NEWTONS PARTICLE THEORY OF LIGHT
Light is made up of little particles.
They obey the same laws of physics as other
masses like baseballs and planets.
They are tiny so the particles in two
intersecting beams do not scatter off each other.
19
PARTICLE THEORY OF REFRACTION
A light particle deep within a medium experiences
no net force.
Near an interface, e.g. between air and water,
light particles experience an attractive force
towards the water.
Could this be the cause of refraction?
20
qi
vair
air
water
qr
vwater
21
NEWTONS EXPLANATION OF SNELLS LAW
sin(qi) vpar/vair
sin(qr) vpar/vwater
sin(qi)/sin(qr) vwater/vair
22
OTHER PROPERTIES
Colors
Polarization
23
Decisive Test of Particle Theory
fixed mirror
source
rotating mirror
air
water