Physical Optics

Question 1

Diffraction

-Types

Answer 1

Bending of waves around obstacles, limits resolution
Component of pinhole acuity
Fraunhofer: far field diffraction
Fresnel: near field diffraction

Question 2

Airy’s Disk

Answer 2

Best focused spot of light a circular aperture can make
Sine grating
Larger Disk = Smaller aperture

Question 3

Rayleigh’s Criteria

Answer 3

Minimum resolvable distinction b/t two Airy disks
sin r = 1.22 (wavelength) / diameter (Circular Aperture)
sin r = (wavelength) / diameter (Single Slit)

Question 4

Equation estimating pinhole acuity

Answer 4

MAR = 2.33 / pinhole diameter (in mm)

-Uses Rayleigh’s criterion

Question 5

Principle of an AR coating

Answer 5

Provides destructive interference via a film with an n more than air but less than the lens behind it

Question 6

Minimum thickness for an AR film

Answer 6

d (thickness) = wavelength / 4n(film)
Optical thickness = d x n(film) may be given
Use 555nm if wavelength is not given

Question 7

Ideal AR film material

Answer 7

n(film) = SQrt of n(media) x n(lens)

Question 8

Rayleigh Scattering

Answer 8

Gives red/orange colors during sunset and blue color to sky
Wavelength DEpendent
Intensity = 1 / Wavelength^4

Question 9

Tyndall Scattering

Answer 9

Gives white appearance of clouds
Occurs when light passes through a suspension causing scattering of shorter wavelengths more than longer ones
Wavelength DEpendent

Question 10

Polarized Light (3 ways)

Answer 10

Oscillations of E vector
Linear: Magnitude changing, constant direction
Circular: Magnitude constant
Elliptically: Magnitude changing

Question 11

Brewster’s Law and use

Answer 11

At some angle at an interface, the light reflected is perpendicular to the light refracted
tan0 = n2/n1
Applied to polaroid sunglasses to reduce horizontal glare

Question 12

Intensity of light transmitted through a polarizer

Answer 12

Unpolarized light use I = 1/2 (I of incident light)
Polarized light use I = (I of incident light) (cos angle b/t)^2
-MALUS Law (simplified to 1/2 (incident light) if angle is 45)

Question 13

UV-ABC wavelengths

Answer 13

UV-A: 400-315 (transmission by lens decreases with age)
UV-B: 315-280
UV-C: 280-100

Question 14

Population Inversion

Answer 14

Majority of atoms in excited state, achieved by pumping energy into the system
-Initiates photon chain reaction in lasers

Question 15

Stimulated Emmision

Answer 15

A released photon from an atom falling to an intermediate (metastable) state causes release of other photons

Question 16

Confocal Scanning Laser Tomography (CSLT)

Answer 16

3-dimensional photographs of the optic nerve and surrounding retina
-images retinal surface
Heidelberg Retinal Tomograph

Question 17

Scanning Laser Polarimetry (SLP)

Answer 17

Measures RNFL thickness by measuring change in polarization

GDxVCC

Question 18

Optical Coherence Tomography

Answer 18

Measures RNFL thickness via temporal delay

Question 19

Speckle Effect

Answer 19

If you shine a coherent beam on a wall, it appears to have speckles due to interference with other beams.
If you move your head the speckles move too
Hyperope: with motion
Myope: against motion

Question 20

Argon Laser Applications

Answer 20

PRP!!

ALT, LPI, retinal tears

Question 21

Excimer Laser Application

Answer 21

LASIK and PRK (photoablation)

-IOP lowers

Question 22

LASIK Ablation depth

Answer 22

250 microns of stroma need to be preserved
12 microns per diopter (from Munnerlyns equation 1/3diameter^2)
40% larger ablation depth for wavefront guided LASIK (15 microns)
-USE 15

Question 23

Nd YAG Applications

Answer 23

YPC for PCO
LPI
SLT (q switched)

Question 24

Helium Neon Laser Applications

Answer 24

retinal illumination

Question 25

Krypton Laser Applications

Answer 25

PRP

similar to argon

Question 26

Holmium Laser Applications

Answer 26

Laser sclerotomy in trab Sx