Aberrations, Camera, Eye

This is a question that we probably can't answer. If the Invisible Man is also blind because no light is being absorbed by his retinas, then when we die and become spirits that are invisible to the naked eye, would our spirit bodies not able to see by physical light? I'm sure that's not a question we can answer at the moment, but this has me wondering now.

I would classify this as “Physics beyond the standard model.”

Am I qualified to work as an optician or optometrist now? I hope my optometrist is more qualified than you….

Now I know what shutter speed is and why it is important. I'm going to go buy a camera! Photography is more fun when you know what you are

doing.

It was nice to understand what the meaning of the number for my glasses is.

The human eye is just so fascinating! Now learning more about optics and just how sensitive and how the eye is able to focus and adjust so efficiently and phenomenally.

For the above ray diagram the mirror is _________ and the image is ___________: A) concave, real B) concave, virtual C) convex, real D) convex, virtual E) flat, imaginary

For the above ray diagram: A)p>0, q > 0, f > 0 B) p>0, q < 0, f > 0 C)p>0, q > 0, f < 0 D)p>0, q < 0, f < 0

For the above ray diagram the lens is _________ and the image is ___________: A) diverging, real B) diverging, virtual C) converging, real D) converging, virtual E) flat, imaginary

For the above ray diagram: A)p>0, q > 0, f > 0 B) p>0, q < 0, f > 0 C)p>0, q > 0, f < 0 D)p>0, q < 0, f < 0

(Quick Quiz 36.3) Consider the image in the mirror. Based on the appearance of the people, would you conclude that: A. The mirror is concave and the

image is real? B. The mirror is concave and the

image is virtual? C. The mirror is convex and the

image is real? D. The mirror is convex and the

image is virtual?

Is it possible to have a virtual object?

A) Yes, trivially. Just set p < 0.

B) No, don’t be silly. The object has to be on the left of the lens/mirror: p > 0 always.

C) I wouldn’t have thought so, but since you are asking the answer must be yes.

Image of one becomes object of next

Worked problem: Find qfinal, Mtot

60 cm 45 cm

f = 20 cm

f = -60 cm

Answers: image is 12 cm to left of -60cm lens; M = -0.4

Image of one becomes object of next

Worked problem: Find qfinal, Mtot

60 cm 15 cm

f = 20 cm

f = -60 cm

Answers: image is 20 cm to right of -60cm lens; M = -0.67

Credit: the next several slides were produced by Dr. Durfee

Aberration caused by Parabolic Mirrors

Incoming light is not parallel to principle axis

Images appear to have a tail (like a comet)

Red light coming from O produces an image at I. Where will blue light coming from O form an image?

A. same place

B. closer to the lens

C. farther from lens 1 2

1 1 11n

f R R

Lens-makers’ eqn:

Chromatic Aberration

For each aberration you should know:

1. What is the causes the aberration and when it might be important to consider

2. Ways of correcting the aberration.

If the camera is initially focused on a distant object, to focus on a close object , must the lens be moved away from the CCD or moved toward the CCD?

According to the lens equation, as p decreases, q will increase (because the sum of their inverses remains constant). So the image will form farther back, which implies that the lens should be moved away from the CCD, toward the object.

f# = The focal length divided by the diameter of the lens

Expressed at f/2.2, f/2.8, etc.

How does the f-number of a lens relate to the half-angle of the “light cone” formed by parallel light entering the lens?

A.

B.

C.

D.

E.

q

1 1tan

2 f-numberq

1tan f-numberq

1 12cos

f-numberq

1 1sin

f-numberq

1sin f-numberq

Suppose you are comparing two cameras which both use the same size sensor and the same zoom level. One of them gives the aperture specification as "f/2.8" whereas the other one is "f/2.2". Which one allows more light to reach the sensor? (Or do they allow the same?)

The camera with the smaller f-number has a larger aperature with a more open lens and thus allows more light into the camera's CCD.

F2.2 lets in more light because it is a bigger hole than f2.8.

f/2.8 is the longer shutter time and allows more light in.

If the shutter time is a constant, then f/2.2 lets in more light.

If you have trouble seeing things far away but can see close objects well, you are “near-sighted”. What kind of lenses do you need in your glasses?

A. Converging lenses

B. Diverging lenses

Far point: how far away can you focus on things

Regular person: fp = infinity

Nearsighted person: fp = much smaller

Near point: how close can you see things comfortably

Regular person: np 25 cm

Farsighted person: np = much larger

How to fix things with glasses?

Farsighted: object at 25 cm image at –np (converging lens)

Nearsighted: object at cm image at –fp (diverging lens)