The nature of light
Reflection
 Refraction


 Index of refraction



Huygens’ Principle
Dispersion and Prisms
Total Internal Reflection

Light as Particles
 Tactile Theory (Ancient Greeks)
 Emission Theory (al-Haitham)
 Newton

Light as Waves (w, k)
 Huygens
 Maxwell

Quantum Theory (E = hf)
 Photons
w  27.5rev / s
t
 1 720

 5.05 105 s
w 27.5
c
2d
27500m
8


2
.
97

10
m/ s
5
t
5.05 10 s
Nteeth  360
d  7500m
Specular Reflection
Diffuse Reflection
1  1
sin  2 v2
  constant
sin 1 v1
Suppose the sprinters wish to get from point Q on the
beach to point P on the parking lot as quickly as possible.
Which path takes the least time?
1. a
2. b
3. c
4. d
5. e
6. All paths take the same
amount of time.
Speed of light in vacuum c
n

Speed of light in medium v
Going from one medium to another, the frequency of light does
not change but its wavelength does.
1 v1 c n1 n2
 

2 v2 c n2 n1
If one of the medium’s is vacuum (n=1),
Snell’s Law of Refraction

n
n
n1 sin 1  n2 sin  2
n1
sin  2  sin 1
n2
h
n2
sin  3  sin  2
n1
n2 n1
sin 3 
sin 1  sin 1
n1 n2
1
x
h
cos  2
2 
d  x sin 
x
  1   2
h
d
d
h
sin 1   2 
cos  2
sin 1 
AC
AC
sin 1 
AC  AD
1  1
sin 1 
v1t
AC
sin  2 
v2 t
AC
sin 1 v1 c n1
 
sin  2 v2 c n2
n1 sin 1  n2 sin  2
AD
AC
: angle of deviation
n  n 

2 
2
 d min
1   2    
2
2
dmin
sin 1  n sin  2
   d min
sin
2



  n sin 

2
   d min 
sin 

2


n
sin  2

d
1
2
3
4
d  1   2    4   3 
d  1   4   2   3 
 2  3  
d  1   4  
Critical Angle, c
n1 sin c  n2 sin 90
n2
sin  c 
n1
Only for n1 > n2
n2
1
sin  c 

 0.752
n1 1.33
 c  48.8
For  < c: The fish sees above
the water
For  = c : The fish sees the
shoreline
For  > c : The fish sees the
pond bottom
Retroreflector
Periscope
Fiber Optic Cable

Reading Assignment
 Chapter 36: Image Formation

WebAssign: Assignment 13