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OPT 111 > Midterm 1 > Flashcards

Midterm 1 Flashcards

1
Q

What is refraction?

A

Bending of light rays due to speed of light in different media

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2
Q

What is Index of Refraction?

A

Equation that describes how much light is slowed down.
n = c / Vm
n = index of refraction
c = how fast light is traveling in air
Vm = how fast light is traveling in medium

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3
Q

What is the speed of light for air?

A

3 x 10^8 m/s (“c”)

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4
Q

How much do lenses typically slow light?

A

1/4 to 1/2 the speed of light in air

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5
Q

What is the index of refraction for ophthalmic lenses?

A

About 1.40 - 2.00
Most common = 1.5/1.6

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6
Q

What is the Rectilinear Propagation of Light?

A

The theory that light will travel in a straight line unless stopped by something

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7
Q

What does Snell’s Law state?

A

That light will bend when crossing from medium #1 to medium #2

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8
Q

What is an object?

A

Anything that gives off light and can be viewed.
Can be an original source of light or seen by light reflecting off of it.

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9
Q

What does an object send light into?

A

A lens

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10
Q

What is a point object/point source?

A

Light source that is very small or appears to be very small

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11
Q

What do point sources emit?

A

Light waves (or energy) equally in all directions.

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12
Q

What is a ray?

A

Drawn perpendicular to light wavefronts and are represented by arrows.
Don’t actually exist.

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13
Q

What is a pencil?

A

2 dimensional collection of rays.

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14
Q

What is a beam of light?

A

3D, cone-shaped bundle of rays.

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15
Q

How does radius of curvature affect wavefront?

A

The shorter the radius, the curvier the surface.
The longer the radius, the flatter the surface.
(the farther the wavefront travels from the point source, the flatter the wavefront becomes)

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16
Q

What is a divergent ray/pencil?

A

The width increases as they move away from the focus point.
Illustrate wavefronts getting flatter.

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17
Q

What is an aperture?

A

Circle that light can go through; can’t go outside of it.

18
Q

What is optical infinity?

A

When divergence is so small it is insignificant.
20 feet.

19
Q

What is a converging ray/pencil?

A

The width decreases as they move toward a focus point.
Illustrate wavefronts getting curvier (steeper).

20
Q

What does a lens do?

A

Changes divergence or convergence

21
Q

What is an extended object?

A

Anything with a measurable size.
Has an infinite number of point sources and is represented by an arrow.
Etc. bulbs, TV screens, people, dogs, etc.

22
Q

What is a real object?

A

Diverging rays into optical system

23
Q

What is a virtual object?

A

Converging rays into optical system

24
Q

What is a virtual image?

A

Diverging rays out of optical system

25
Q

What is real image?

A

Converging rays out of optical system

26
Q

What is a physically real image?

A

Rays make it to the point of conversion.

27
Q

What happens if rays pass through a lens before reaching the screen?

A

Still a physically real image because the rays make it to the screen, but the image will be blurry

28
Q

What is an optically real image?

A

Converging rays cannot make it to the point of conversion.

29
Q

What is vergence?

A

Amount of divergence or convergence of light waves.
Related to the curvature of the wavefront at a given point.

30
Q

What is index of refraction for air?

A

1.00

31
Q

What is the diopter?

A

Reciprocal of the distance you are away from a point source (divergent rays).
Reciprocal of the distance from point focus (convergent rays).

32
Q

What does a shorter/longer radius curvature mean in terms of vergence?

A

Shorter radius curvature = more vergence.
Longer radius curvature = less vergence.

33
Q

Where is vergence infinite?

A

At the point source for divergent rays.
At the focus point for convergent rays.

34
Q

What is the vergence equation?

A

L = n / l

35
Q

What is the unit for vergence?

A

meters

36
Q

Do diverging rays have a positive or negative vergence?

A

Negative because light rays always diverge (go away from) a real object

37
Q

What happens to the vergence when you double the distance?

A

Half the vergence

38
Q

What is the common index value of air?

A

1.00

39
Q

What is the common index value of water?

A

1.33

40
Q

What is the common index value of CR-39 plastic?

A

1.49

41
Q

What is the common index value of crown glass?

A

1.523

OPT 111 (2 decks)

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