2. Classical Interferometry

Question 1

What are two popular models describing the nature of light?

Answer 1

Electromagnetic wave model (EM wave model) Quantum model

Question 2

What are the basic principals of the EM wave model for describing the nature of light?

Answer 2

Light consists of energy in the form of EM waves EM disturbance propagates through space A wave is described by two vectors

Question 3

What are the two vectors describing a wave in the EM wave model for describing the nature of light?

Answer 3

E - electric vector H - magnetic vector

Question 4

What are some of the shortcomings of the EM wave model for describing the nature of light?

Answer 4

Predicts infinite energy for small wavelengths No clear expression for nature of light Doesn’t provide an explanation for some phenomena (e.g, photoemission)

Question 5

What are the basic principals of the quantum model for describing the nature of light?

Answer 5

Light consists of ‘bundles’ or photons of energy Behavior of photons is described using statistical mechanics

Question 6

When is EM wave theory applicable?

Answer 6

For long waves (wavelengths up to around 1m) For light waves (wavelengths between 1mm to 1nm)

Question 7

When is the Quantum model applicable?

Answer 7

For light waves (wavelengths between 1mm to 1nm) For short waves (down to around 1A (0.1nm))

Question 8

What is the application of long waves? (around 1m)

Answer 8

Long waves are radio waves

Question 9

What is the application of light waves (1mm - 1nm)

Answer 9

Light waves range from infrared to UV

Question 10

What is the application of short waves? (around 1A)

Answer 10

Short waves are x-rays

Question 11

What are Maxwell’s Equations based upon?

Answer 11

Based on wave theory by Coulomb and Faraday Relies on 4 constitutive equations to lay out a set of rules defining interaction of electromagnetic waves with matter

Question 12

What are the field parameters for Maxwell’s equations?

Answer 12

E, Electric vector H, Magnetic vector (E and H define EM field) D, Electric displacement vector J, Current density vector B, Magnetic induction vector (D,J and B are field quantities)

Question 13

For a non conducting medium that is free of electric charge what must electric vector E satisfy?

Answer 13

ε is dielectric constant, µ is magnetic permeability, c is speed of light (or light wave)

Question 14

For a harmonic plane wave propagating in the z-direction what is the equation for electric vector E?

Answer 14

A = amplitude of wave

v = c /√(ε µ ) = speed of propagation

λ = wavelength of light

Question 15

Draw out a monochromatic, linarly polarised light wave undergoing simple harmonic vibration

Answer 15

Question 16

What is Irradiance?

Answer 16

Time averaged square of amplitude, measureable by photo sensors

Question 17

What is the frequency for any given wave?

Answer 17

Question 18

What are the lhe wavelenths for the different catagories of light?

Answer 18

Question 19

What is the generalised equation for a wave propagating along some axis in terms of the electric vector?

Answer 19

Question 20

What is the unit position vector?

Answer 20

l, m and n are directional cosines

Question 21

What is the general position vector?

Answer 21

l, m and n are directional cosines

Question 22

What is the generalised equation for a wave propagating along the z axis with an added phase shift, in terms of the electric vector?

Answer 22

ϕ is a phase shift

ϕ and A can vary in the spatial domain

terms regarding time can be disgarded as the optical frequencies cannot be detected

Question 23

What do the electric vecotor, E and Magnetic vector, H define?

Answer 23

The EM field

Question 24

Draw out a warped wavefront?

Answer 24

Question 25

Draw out a plane wavefront

Answer 25

ϕ = constant = zero

Question 26

Draw a x-section of a spherical wave

Answer 26

Question 27

Spherical Wavefront
What is the electric vector equation for light radiating from a true point source?

Answer 27

Question 28

How is a spherical wavefront generated?

Answer 28

By passing a plane wave through a lens

Question 29

Interference of Collinear Waves

Draw out 2 coherewent waves travelling in the z-direction of the same wavelength, velocity and polarisation

Include equations

Answer 29

Question 30

Combined wave

What is the electric vector equation for a combined wave?

Answer 30

Assumes amplitudes are equal

Circled is the complex amplitude of combined wave

Question 31

Fringe formation

What is the equation for irradiance?

Answer 31

Question 32

Fringe Formation

When does constructive interference happen?

When does destructive interference happen

When do you get poor fringe contrast

Use a diagram if helpful

Answer 32

Question 33

Interference of plane waves?

Draw out 2 coherent waves propagating along axes α1 and α2

Include the equation for the electric vector regarding this

Answer 33

Question 34

Interference bands

Write out the Irradiance equation for intereference bands

Answer 34

Question 35

Interference bands

What does the circled term depend on?

Answer 35

Incidence angles

Wavelengths

Initial phases

Position of observation

Question 36

Fringe Properties

What do all the terms in this picture refer to

Answer 36

ζ = angle of incidence

λ = Wavelength

Dp = Fringe spacing

Question 37

Fringe Properties

What is the equation for fringe visability?

Answer 37

Question 38

Fringe Properties

What is the equation for fringe spacing

Answer 38