Deck 25: Vision and Optical Instruments

Question 1

Explain how the eye and a camera differ in adjusting for a change in focus.

Answer 1

The camera lens has a fixed focal length so it adjusts focus by varying the lens-film distance. The eye has an essentially fixed lens-retina distance so the focal length of the lens is varied by changing the lens curvature (by muscular action).

Question 2

Choose from the following:

-Match the iris to the best description below.

A) composed of microscopic glassy fibers that slide over each other
B) a jelly-like substance that fills most of the eye
C) a circular diaphragm
D) relays signals to the brain
E) the central hole
F) a curved transparent tissue where light first enters the eye
G) photosensitive receptor cells of which the retina is composed
H) a light-sensitive surface, upon which the image falls

Answer 2

a circular diaphragm

Question 3

Choose from the following:

-Match vitreous humor to the best description below.

A) composed of microscopic glassy fibers that slide over each other
B) a jelly-like substance that fills most of the eye
C) a circular diaphragm
D) relays signals to the brain
E) the central hole
F) a curved transparent tissue where light first enters the eye
G) photosensitive receptor cells of which the retina is composed
H) a light-sensitive surface, upon which the image falls

Answer 3

a jelly-like substance that fills most of the eye

Question 4

Choose from the following:

-Match retina to the best description below.

A) composed of microscopic glassy fibers that slide over each other
B) a jelly-like substance that fills most of the eye
C) a circular diaphragm
D) relays signals to the brain
E) the central hole
F) a curved transparent tissue where light first enters the eye
G) photosensitive receptor cells of which the retina is composed
H) a light-sensitive surface, upon which the image falls

Question 5

Choose from the following:

-Match optic nerve to the best description below.

A) composed of microscopic glassy fibers that slide over each other
B) a jelly-like substance that fills most of the eye
C) a circular diaphragm
D) relays signals to the brain
E) the central hole
F) a curved transparent tissue where light first enters the eye
G) photosensitive receptor cells of which the retina is composed
H) a light-sensitive surface, upon which the image falls

Question 6

Choose from the following:

-Match cornea to the best description below.

A) composed of microscopic glassy fibers that slide over each other
B) a jelly-like substance that fills most of the eye
C) a circular diaphragm
D) relays signals to the brain
E) the central hole
F) a curved transparent tissue where light first enters the eye
G) photosensitive receptor cells of which the retina is composed
H) a light-sensitive surface, upon which the image falls

Question 7

Choose from the following:

-Match pupil to the best description below.

A) composed of microscopic glassy fibers that slide over each other
B) a jelly-like substance that fills most of the eye
C) a circular diaphragm
D) relays signals to the brain
E) the central hole
F) a curved transparent tissue where light first enters the eye
G) photosensitive receptor cells of which the retina is composed
H) a light-sensitive surface, upon which the image falls

Question 8

Choose from the following:

-Match rods and cones to the best description below.

A) composed of microscopic glassy fibers that slide over each other
B) a jelly-like substance that fills most of the eye
C) a circular diaphragm
D) relays signals to the brain
E) the central hole
F) a curved transparent tissue where light first enters the eye
G) photosensitive receptor cells of which the retina is composed
H) a light-sensitive surface, upon which the image falls

Question 9

Choose from the following:

-Match lens to the best description below.

A) composed of microscopic glassy fibers that slide over each other
B) a jelly-like substance that fills most of the eye
C) a circular diaphragm
D) relays signals to the brain
E) the central hole
F) a curved transparent tissue where light first enters the eye
G) photosensitive receptor cells of which the retina is composed
H) a light-sensitive surface, upon which the image falls

Question 10

Many Earth-based telescopes are larger than the Hubble Space Telescope, so what justifies the great expense of a "space-based" instrument?

Question 11

Both the microscope and the telescope make the object appear much larger. Why are these two instruments designed differently (e.g., why are the equations for magnification quite different)?

Question 12

How is it possible for the angular magnification to be large and, at the same time, for the lateral magnification to be small? Give an example.

Question 13

Astigmatism is usually due to

A) the cornea or lens being out of round.
B) accommodation.
C) hyperopia.
D) missing rods.
E) myopia.

Question 14

If a person's eyeball is too long from front to back, the person is likely to suffer from

A) farsightedness.
B) spherical aberration.
C) astigmatism.
D) nearsightedness.
E) chromatic aberration.

Question 15

If a person's eyeball is too short from front to back, the person is likely to suffer from

A) spherical aberration.
B) nearsightedness.
C) farsightedness.
D) chromatic aberration.
E) astigmatism.

Question 16

The near point with age usually

A) steadily decreases.
B) steadily increases.
C) increases and then decreases.
D) approaches 25. cm.

Question 17

Nearsightedness can usually be corrected with

A) cylindrical lenses.
B) diverging lenses.
C) converging lenses.
D) achromatic lenses.

Question 18

The principal refraction of light by the eye occurs at the

A) cornea.
B) retina.
C) sclera.
D) lens.
E) iris.

Question 19

"30/40 vision" is a measure of

A) visual acuity.
B) chromatic aberration.
C) eyeball size.
D) astigmatism.
E) the resolution of the eye.

Question 20

Farsightedness can usually be corrected with

A) converging lenses.
B) cylindrical lenses.
C) achromatic lenses.
D) diverging lenses.

Question 21

If the human eyeball is too short from front to back, this gives rise to a vision defect that can be corrected by using

A) concave-convex eyeglasses.
B) convex-convex eyeglasses.
C) shaded glasses (i.e., something that will cause the iris to dilate more).
D) contact lenses, but no ordinary lenses.
E) cylindrical eyeglasses.

Question 22

Rays that pass through a lens very close to the lens axis are more sharply focused than those that are very far from the axis. The inability of a lens to sharply focus off-axis rays is called spherical aberration. This effect helps us to understand why

A) it is easier to read in bright light than in dim light.
B) a moving object is more readily detected than a stationary one.
C) we can see only in black and white in dim light.
D) we become more nearsighted as we grow older.
E) we become more farsighted as we grow older.

Question 23

A fish's eye is well-suited to seeing under water, but what can you say about his vision if he is taken out of water?

A) He would be nearsighted.
B) His vision would be limited to a cone of half-angle of about 49°.
C) He would suffer from astigmatism.
D) He would be farsighted.
E) His acuity (sharpness of vision) would be greater.

Question 24

Angular magnification of a magnifying glass is largest when the image is at

A) the far point.
B) the focal point.
C) the pupil of the eye.
D) the near point.
E) infinity.

Question 25

With what color light would you expect to be able to see the greatest detail when using a microscope?

A) blue, because of its shorter wavelength
B) red, because it is refracted less than other colors by glass
C) blue, because it is brighter
D) red, because of its long wavelength
E) The color makes no difference in the resolving power, since this is determined only by the diameter of the lenses.

Question 26

For relaxed viewing (microscope or telescope) the eyepiece is adjusted to place the image at

A) the near point.
B) infinity.
C) the pupil of the eye.
D) the focal point.
E) the radius of curvature.

Question 27

Jennifer bought a 7 × 25 pair of binoculars for observing baseball. The 25 describes the

A) magnification.
B) f/number.
C) aperture in mm.
D) aperture in cm.
E) (f/number)^-1

Question 28

Christie bought a 9 × 50 pair of binoculars for stellar observing. The 9 is the

A) (f/number)^-1
B) aperture in mm.
C) f/number.
D) aperture in cm.
E) angular magnification.

Question 29

The resolution limit of a circular aperture telescope is

A) proportional to frequency of light.
B) inversely proportional to aperture size.
C) less than that of a square aperture whose diagonal equals the diameter.
D) inversely proportional to wavelength.

Question 30

The resolving power of a microscope refers to the ability to

A) form a very bright image.
B) distinguish objects of different colors.
C) form a very large image.
D) form clear images of two points that are very close together.
E) form a very microscopic image.

Question 31

If the diameter of a radar dish is doubled, what happens to its resolving power assuming that all other factors remain unchanged?

A) It quadruples.
B) It is reduced to one-quarter its original value.
C) It doubles.
D) It halves.
E) It is reduced to one-eighth its original value.

Question 32

A person gazes at a very distant light source. If she now holds up two fingers, with a very small gap between them, and looks at the light source, she will see

A) the same thing as without the fingers, but dimmer.
B) a sequence of closely spaced bright lines.
C) a series of bright spots.
D) a hazy band of light varying from red at one side to blue or violet at the other.

Question 33

Which cones on the eye are most sensitive to light?

A) UV
B) red
C) infrared
D) blue
E) green

Question 34

If you wear green sunglasses and look at equations written in white chalk on a chalkboard, you would see the chalk as

A) green.
B) red.
C) white.
D) yellow.
E) black.

Question 35

Color blindness is caused by

A) a missing rod-type.
B) lack of melanin.
C) cataracts.
D) damage to the retina.
E) a missing cone-type.

Question 36

Color TV is produced by

A) A single beam of electrons striking a triad of phosphors of cyan, magenta, and yellow.
B) red, green, and blue beams of electrons merging at the screen.
C) A single beam of electrons striking a triad of phosphors of red, green, and blue.
D) cyan, magenta, and yellow beams of electrons merging at the screen.

Question 37

If a red filter were placed in front of blue dungarees, you would see

A) green.
B) red.
C) white.
D) black.
E) blue.

Question 38

Mixing pigments is an example of the ________ method of color production.

A) "tri-color"
B) subtractive
C) complementary
D) composite
E) additive

Question 39

A nearsighted man wears -3.00 D lenses. With these lenses, his corrected near point is 25.0 cm. What is his uncorrected near point?

Question 40

A hyperopic eye can focus on objects which are 75. cm and farther. What POWER and what FOCAL LENGTH spectacles should be prescribed so it can see objects 25. cm and farther from the eye? (Assume negligible distance between spectacles and eye.)

Question 41

A nearsighted person has a far point of 50. cm for one eye and 150. cm for the other. What power contact lenses allow the person to see distant objects?

Question 42

Mary builds a simple magnifying telescope using two lenses of focal length 80. cm and 5.0 cm. The respective diameters are 60. mm and 10. mm. How many degrees wide does the moon appear through the telescope if it appears only 1/2 degree wide with the "naked eye"?

Question 43

What is the minimum distance of two points on the moon that can be just resolved by the Keck 10. meter telescope in Hawaii (use a wavelength of 600. nm, lunar distance of 380. thousand Km)
(a) if there were no atmosphere?
(b) if the atmosphere limits resolution to 0.2 arc-sec?

Question 44

Consider a camera with a 20. cm diameter lens recording images at 600. nm wavelength.
(a) What is the angular resolution limit?
(b) What is the minimum sized features which can be resolved on Mars (at a distance of 9.0 × 10⁷ km) with this lens?

Question 45

The near point of a farsighted person is 100 cm. She places reading glasses close to her eye, and with them she can comfortably read a newspaper at a distance of 25 cm. What lens power is required?

A) -2.5 D
B) +2.5 D
C) +3.0 D
D) -2.0 D
E) +3.2 D

Question 46

What power lens is needed to correct for farsightedness where the uncorrected near point is 75 cm?

A) +2.67 D
B) +1.00 D
C) +5.33 D
D) -2.67 D
E) -5.33 D

Question 47

What power lens is needed to correct for nearsightedness where the uncorrected far point is 75 cm?

A) +1.33 D
B) -1.00 D
C) -0.75 D
D) +0.75 D
E) -1.33 D

Question 48

Kelli examines her new ruby ring with the jeweler's "loop". The ruby appears 7.0 times larger. If her near point is 35. cm, what is the focal length of the lens?

A) 42. mm
B) 67. mm
C) 70. mm
D) 36. mm
E) 58 mm

Question 49

Which of the following binoculars would be best for observing very faint comets among the stars?

A) 12 × 50
B) 7 × 60
C) 8 × 50
D) 5 × 20
E) 10 × 35

Question 50

A telescope has an angular magnification of 250. when operated with a 20. mm eyepiece. What is the focal length of the objective?

A) 5.0 meters
B) 25. meters
C) 5.0 cm
D) 2.5 m
E) 5000. cm

Question 51

Pat is viewing the moon with her new telescope. She is using a 10. mm eyepiece. Which of the following eyepieces will double the magnification?

A) 8. mm
B) 200. Diopter
C) 12. mm
D) 40. Diopter
E) 5. Diopter

Question 52

Assuming a pupil diameter of 3. mm, what is the angular resolution of the human eye at the middle of the visible spectrum (550. nm)?

A) 0.2 arc-minute
B) 0.8 arc-minute
C) 0.2 degree
D) 2. milliradian
E) 0.8 degree

Question 53

Using the Rayleigh Criterion for 400. nm light, what sized space telescope could have 1.0 km resolution of objects on Mars when viewed from above the Earth? (assume an Earth-Mars close distance of 80. million km)

A) 39. km
B) 3.9 m
C) 3.9 km
D) 39. m
E) 0.39 km