Nature of Light and Laws of Geometric Optics

1
Nature of Light and Laws of Geometric Optics

• The nature of light
• Reflection
• Refraction
• Index of refraction
• Huygens Principle
• Dispersion and Prisms
• Total Internal Reflection

2
The Nature of Light

• Light as Particles
• Tactile Theory (Ancient Greeks)
• Emission Theory (al-Haitham)
• Newton
• Light as Waves
• Huygens
• Maxwell
• Quantum Theory
• Photons

3
Fizeaus Method for Speed of Light Measurement
4
Ray Approximation in Geometric Optics
5
Reflection
Specular Reflection
Diffuse Reflection
6
Double Reflection
7
Refraction
8
Concept Question
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.

9
Index of Refraction
Going from one medium to another, the frequency
of light does not change but its wavelength does.
If one of the mediums is vacuum (n1),
Snells Law of Refraction
10
Announcements

• Cell phones on silent.
• Fermats principle nothing quantitative just
  understand the idea of minimum time.

11
Light Propagation Through a Slab
q1
a
q2
h
x
d
12
Huygens Principle
13
Huygens principle Plane waves
14
Huygens principle diffraction
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Huygens Principle Applied to Reflection and
Refraction
16
Dispersion and Prisms
angle of deviation
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Measuring n Using a Prism
dmin
18
Angle of Deviation
a
d
q4
q1
19
Total Internal Reflection
Critical Angle, qc
Only for n1 gt n2
20
View From a Fish Eye
For qltqc The fish sees above the water For qqc
The fish sees the shoreline For qgtqc The
fish sees the pond bottom
21
Applications of TIR
Retroreflector
Periscope
Fiber Optic Cable