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43 Cards in this Set

  • Front
  • Back
What happens to the wavefront as it approaches infinity?
The wavefront flattens out as it approaches infinity?
At what distance do we say the eye can’t really distinguish between this and infinity?
~6m or 20ft
What is the speed of light?
~3x10^8

299,792,458m/s
Is light reversible in a system?
Yes
What is one way that we can get parallel light into a system?
Setting up a lens system.
What do rays from a common point form?
A pencil
What are the 3 types of pencils?
-Divergent pencil

-Convergent pencil – usually only happens with a lens

-Parallel pencil
What is the chief ray?
The ray that passes through the center of the pupil.
What is a beam?
The sum of all the pencils (w/ an extended source)
What is a real image point?
Where the rays converge into one point.
Where do we want the real image point to be in the eye?
To form on the retina.
What is Vergence?
The reciprocal of the distance from a reference point to the point of focus.

Vergence = 1/d
What is the standard unit of measurement for vergence when measured in meters?
Diopter
In the real world, does a real object have a positive or negative vergence?
Negative
When a lens/convergence is used, do you get positive or negative vergence?
Positive
Is a vergence scale linear?
NO
What are 2 methods for calculating Vergence?
-Distances

-Step along and Step Back
What is the formula for Step along and Step Back?
-it is different depending what direction you are going relative to the light.
Going with the light

Ly = Lz / ( 1+|d|x Lz )

Going against the light

Ly = Lz / ( 1-|d|x Lz )
If vergence of light at a position is measured to be a negative value in diopters, is it converging or diverging light?
Diverging
If vergence of light at a position is measured to be a positive value in diopters, is it converging or diverging light?
Converging
What is an Umbra?
A full shadow
What is a Penumbra?
Partial shadow
What are the two types of light sources and which one exists in the real world?
-Point source - non real world, like an aperture

-Extended source – real world
Does a long or shorter Axial Length give a bigger shadow?
A long axial length gives a bigger shadow – sucks for myopes.
Is the junction between umbra and penumbra a sharp contrast?
Not usually, it gradually decreases in shadow as you move out from the umbra/penumbra line
What is a good way to calculate shadow?
Using triangles and complementary bases.

B1/H1 = B2/H2
What does light reflect off of?
All surfaces!
In reflection, how does the angle of incidence relate to the angle of reflection? (on a flat surface)
They are equal!
What is the Incident ray?
The incoming ray.
What is the reflected ray?
The outgoing ray.
What is refraction?
When a light ray bends due to going from one substance to another with different refractive indexes.
When light goes from a Low to High index, how is the light refracted?
The refracted ray bends toward normal
When light goes from a High to Low index, how is the light refracted?
The refracted ray bends away from normal
How is a Normal (0 degrees) incident ray refracted?
It isn’t, it passes straight through undeviated.
Snell’s law is used to describe how light reacts when moving through different objects with different refractive indexes. What is Snell’s Law?
N1 sin ᶱ 1 = N2 sin ᶱ 2
How is the refractive index of a substance figured?
N substance = Vlight in a vacuum / Vlight in the substance
When light passes through a block, how does the emergent ray compare to the incident ray?
The emergent ray is at the same angle as the incident ray, but it is displaced some amount depending on the depth of the block and its refractive index.
When light passes through multiple blocks, how does the emergent ray compare to the incident ray?
The emergent ray is at the same angle as the incident ray, but it is displaced some amount depending on the depth of the block and its refractive index.
What is the formula for apparent depth?
Dapparent = d / n
What is the formula for apparent displacement?
Apparent displacement = d ( 1 – ( 1 / n ))
What is a Critical angle in refraction?
It is the minimum angle where no light passes through, but is instead totally reflected
What is the formula for Critical Angle
It’s still Snell’s law

N1 sin ᶱ 1 = N2 sin ᶱ 2

Sin 90 = 1
What is the angle of refraction of the Critical Angle?
90 degrees