Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
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
|