Optics: Block 4 Flashcards
Incoherent scattering depends not on…
Speed of light
Which scattering happens with absorption of light?
Rayleigh Scattering
What is the scattering profile of Mie Scattering?
Mostly forward
Bluer light means there will be more scattering? T/F
True
Corneal transmittance is dependent on what?
Wavelength
Which refractive surgery techniques cause an increase of intraocular scatter by a factor of 2 with an 8 mm pupil?
Radial (RK)
What’s the effective light transmission of red light in blue eyes?
1%
What’s the effective light transmission of green light in blue eyes?
0.2%
Blue/Blue-green eyes have intraocular scatter caused by what?
- Pigmentation in scleral walls
- Iris
- Fundus
Pt comes in with a healthy non-cataractous eye. Intraocular scatter increases by 2 times at the age of what, compared to young eyes?
65 years
How many fringes will there be between the central maxima and the first order for a slit at 400 nm wavelength?
# fringes = n-2 = 400-2 = 398
**diffraction on multiple slits
In accordance with phase change, what does coherence mean?
Ability for 2 waves to stay together
In accordance with phase change, what does coherence light mean?
Length for 2 waves to travel together
In accordance with phase change, what does coherence time mean?
How long 2 waves stick together
What determines thin film interference?
- Division of amplitude (aka intensity)
- Change in refractive index has to increase (go from a smaller refractive index to a larger refractive index
What is one factor that doesn’t change when switching mediums?
Frequency
What are the factors that change when changing mediums?
Wavelength and Speed of light
When two waves are traveling in opposite directions, what is this known as?
Destructive Interference (out of phase)
When two waves are traveling in the same directions, what is this known as?
Constructive interference (in phase)
When is the only time you can have a phase change?
When the light is traveling from a lighter medium to a denser medium (lower refractive index to higher refractive index)
Wave 1 and 2 are in phase. wave 1 travels an extra distance (or path difference) equal to 1 wavelength. What is it now?
Constructive interference
Condition for destructive interference is when the path difference (funny s looking greek letter) between 2 waves is equal to what?
(m+1/2)(wavelength)
In a condition for forming bright fringes, dsin(theta)=m(lambda), ‘d’ represents distance between 2 slits and the screen. T/F
False (d = the distance between the slits)
He-Ne Laser (lambda=632.8nm); double slits of 8mm separation; L=6m (distance between the slits and the screen); How far is the 3rd order maximum from the center of interference pattern?
asin(theta)=m(lambda) =3(632.8nm) (0.008)(y/6)=1.89x10^-4 y=0.014175 =14.2mm
2 conditions for interference fringe in Young’s Double slit?
- Monochromatic light
- Coherent light
Thin film interference is based on amplitude divisions? T/F
True
Young’s double slit is based on what?
Wavelength
Common single layer anti-reflection coating material?
Magnesium fluoride
Single layer anti-reflection coating reduces light reflection from what percentage or what percentage?
4.3% to 1.5%
How much does a multilayer anti-reflection thin film coating reduce light reflection to about?
=0.5%
Minimum thickness of anti-reflecting thin film on glass is ___ of wavelength in thin film.
Quarter (t=lambda/4)
Diffraction is the change in direction of propagation due to what?
Edge phenomenon
Using Fresnel, secondary wavelets would undergo mutual interference. T/F
True
Condition interference for single slit diffraction
asin(theta)=m(lambda)
Single slit diffraction; aperture size (a) decreases; diffraction pattern does what?
Spreads out
Condition interference for thin film?
2t=m(lambda)
Type of diffraction if the source of light and screen are at finite distance from the diffraction aperture.
Fresnel
Smallest letters a person with 20/40 acuity can resolve have details that sub tends at an angle of what?
2’
Optical device that blocks alternate zones is called what?
Zone plate
What happens to the diffraction image point in the phase plate when the alternate zones are phase shifted 180 degrees?
Gets BRIGHTER
Incoherent scattering depends on what 2 conditions?
- Particle size
- Distance between the 2 particles (greater than coherence length of light…how how long they can stick together)
When particles are smaller than wavelength of light, you get what scattering?
Rayleigh Scattering
How does scattering of Mie scatter appear?
Particles are bigger than wavelength and mostly forward
How does scattering of Rayleigh scatter appear?
Particles are in most all directions
Shorter wavelength of light will scatter more. T/F
True
What color of light will scatter more?
Blue
Corneal transmittance is dependent on what?
Wavelength
What is the effective light transmission of the iris for red light if the iris appears blue?
=1%
What is the effective light transmission of the iris for green light if the iris appears blue?
=0.2%
What are the three contributors for blue and green eyes?
- Scleral wall
- Iris
- Fundus (retina)
What’s the increase of scatter for age of 65 compared to young eyes?
2 times
What’s the increase of scatter for age 75 compared to young eyes?
3 times
What percent of horizontally polarized light gets transmitted if a vertically polarizing filter is tilted 5 degrees?
=0.8%
For a light in air, incident on high index of refraction of plastic (n=1.66), what’s the incident angle of polarization? What incident angle results in 100 percent polarization?
Tan(theta)=n2/n1
Nn2=1.66
=58.9 degrees
A sunlight glare can pass through a polarized filter. What should be the transmission axis when reflecting off a pond or a lake?
Horizontal
Vertical used to block the light coming into the eyes
The waggle dance of the bee communicates what?
- direction of food
- location of food
Form dichroism is based on what?
Structure
When light travels in a bifringent material, a delay between waves is called what?
Phase retardation
An ordinary ray is known as what?
Fast ray
Due to bifringence of the cornea and lens, it changes from linear polarization to what?
Elliptical polarization
Reflection back from the fundus is what type of polarization?
Partial polarization
Heidinger’s brush….the bow tie that can be used to detect and train amblyopia due to what?
Eccentric fixation
