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