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Nature of Light and Laws of Geometric Optics
The nature of lightReflectionRefraction
Index of refraction
Huygens’ PrincipleDispersion and PrismsTotal Internal Reflection
The Nature of LightLight as Particles
Tactile Theory (Ancient Greeks)Emission Theory (al-Haitham)Newton
Light as Waves (ω, k)HuygensMaxwell
Quantum Theory (E = hf)Photons
Fizeau’s
Method for Speed of Light Measurement
srev /5.27=ω
360=teethN
md 7500=
st 51005.55.27
7201 −×===ωθ
( ) sms
mtdc /1097.2
1005.5750022 8
5 ×=×
== −
Ray Approximation in Geometric Optics
Reflection
Specular Reflection Diffuse Reflection
11 θθ =′
Double Reflection
Refraction
constantsinsin
1
2
1
2 ==vv
θθ
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. a2. b3. c4. d5. e6. All paths take the same
amount of time.
Concept Question
Index of Refraction
vcn =≡
mediumin light of Speedin vacuumlight of Speed
Going from one medium to another, the frequency of light does not change but its wavelength does.
1
2
2
1
2
1
2
1
nn
ncnc
vv
===λλ
If one of the medium’s is vacuum (n=1), n
nλλ
=
2211 sinsin θθ nn =Snell’s Law of Refraction
h
Light Propagation Through a Slab1
2
12 sinsin θθ
nn
=
21
23 sinsin θθ
nn
=
112
1
1
23 sinsinsin θθθ ==
nn
nn
h
2cosθhx =
αsinxd =
21 θθα −=
( )212
sincos
θθθ
−=hd
dx
θ2α
θ1
Huygens’
Principle
Huygens’
Principle Applied to Reflection and Refraction
ACCA′
=1sinθ ACAD
=′1sinθ
ADCA =′
11 θθ ′=
ACtv Δ
= 11sinθ
ACtv Δ
= 22sinθ
2
1
2
1
2
1
sinsin
ncnc
vv
==θθ
2211 sinsin θθ nn =
Dispersion and Prisms
( )λnn =
angle of deviation
Measuring n Using a Prism
22Φ
=θ
δmin
22min
21δαθθ +
Φ=+=
21 sinsin θθ n=
⎟⎠⎞
⎜⎝⎛ Φ=⎟
⎠⎞
⎜⎝⎛ +Φ
2sin
2sin min nδ
( )2sin2
sin min
Φ
⎟⎠⎞
⎜⎝⎛ +Φ
=
δ
n
Angle of Deviation
δ
α
θ1
θ4 αθθδ −+= 41
Total Internal Reflection
°= 90sinsin 21 nn cθ
1
2sinnn
c =θ Only for n1 > n2
Critical Angle, θc
View From a Fish Eye
°=
===
8.48
752.033.11sin
1
2
c
c nn
θ
θ
For θ<θc : The fish sees above the water
For θ=θc : The fish sees the shoreline
For θ>θc : The fish sees the pond bottom
Applications of TIR
Retroreflector Periscope Fiber Optic Cable
For Next ClassReading Assignment
Chapter 36: Image Formation
WebAssign: Assignment 13