Question 1

The image area on 35 mm film is 24 mm × 36 mm. What focal length lens of the following will allow an image of the moon, 0.50° in angular size, to just fit on the film?

Accepted Answer

A)   2.8 m
B)   1.4 m
C)   0.85 m
D)   12 mm
E)   55 mm A

Question 2

What kind of images do the two lenses in a compound microscope form?

Accepted Answer

A)   Both lenses form virtual images.
B)   The lens closest to the object forms a real image; the other lens forms a virtual image.
C)   Both lenses form real images.
D)   The lens closest to the object forms a virtual image; the other lens forms real image. B

Question 3

What causes spherical aberration?

Accepted Answer

A)   The lens surface is not perfectly smooth.
B)   The outer edges of the lens produce a focus at a different point than the central rays.
C)   Light is an electromagnetic wave with intrinsic diffraction properties.
D)   The absorption of light in the glass depends on the wavelength. B

Question 4

Two converging lenses, the first with focal length 25 cm and the second with focal length 20 cm, are separated by 30 cm. A 4.0 cm tall object is placed 50 cm in front of the first lens. Where is the image formed by the first lens?

Accepted Answer

A)   17 cm in front of the first lens
B)   50 cm after the first lens
C)   75 cm after the first lens
D)   27 cm after the second lens
E)   50 cm after the second lens

Question 5

A person has his nearsightedness corrected by lenses of refractive power −5.00 D. Without his glasses, his near point was 12.5 cm. With his glasses on, what is his near point? Assume the lenses are very close to his eyes.

Accepted Answer

A)   13.0 cm
B)   20.0 cm
C)   33.3 cm
D)   17.5 cm
E)   7.50 cm

Question 6

A camera with interchangeable lenses produces an image of a distant object that is 3.0 mm wide on the film when the 50.0 mm lens is used. When the 135 mm lens is used, how wide is the image of the object on the film?

Accepted Answer

A)   3.0 mm
B)   85 mm
C)   4.5 mm
D)   0.37 mm
E)   8.1 mm

Question 7

A simple magnifier of refractive power 15.0 D is used to observe a beetle on a student's desk. Assume that the magnifier is held close to the student's eye. If the image of the beetle is twice as large as the beetle itself, how far away is the image formed relative to the lens?

Accepted Answer

A)   6.7 cm
B)   8.3 cm
C)   3.3 cm
D)   10 cm
E)   20 cm

Question 8

Increasing the aperture size on a camera

Accepted Answer

A)   reduces the depth of field and requires a longer exposure time.
B)   reduces the depth of field and requires a shorter exposure time.
C)   increases the depth of field and requires a longer exposure time.
D)   increases the depth of field and requires a shorter exposure time.

Question 9

What magnifying power is attained using a compound microscope with the following specifications: objective focal length 1.50 cm, eyepiece focal length 2.42 cm, tube length 16.0 cm? Assume a near point of 25.0 cm and that the microscope is adjusted for viewing an image at infinity.

Accepted Answer

A)   110
B)   90.0
C)   12.0
D)   11.0
E)   8.00

Question 10

A lens of focal length 10 cm is placed in contact with a lens of focal length −15 cm. What is the focal length of the combination?

Accepted Answer

A)   -15 cm
B)   6.0 cm
C)   7.5 cm
D)   −5.0 cm
E)   30 cm

Question 11

The loss of accommodation that comes with aging is called

Accepted Answer

A)   myopia.
B)   hyperopia.
C)   presbyopia.
D)   retinalopia.
E)   macularopia.

Question 12

A nearsighted person wears contact lenses of refractive power −6.0 D. What is his far point?

Accepted Answer

A)   6.0 cm
B)   −6.0 cm
C)   17 cm
D)   −17 cm
E)   −4.0 cm

Question 13

A camera lens has a fixed focal length of 35 mm. How far must the lens be moved, relative to the image sensor, in order to change the focus from an object that is 20 m away to one that is 3 m away?

Accepted Answer

A)   0.34 mm
B)   0.41 mm
C)   0.35 mm
D)   0.47 mm

Question 14

Two lenses, the first with focal length −12.5 cm and the second with focal length 20.0 cm, are separated by 15.0 cm. If an object is placed 50.0 cm in front of the first lens, what is the total magnification?

Accepted Answer

A)   20.0
B)   −20.0
C)   1.25
D)   −1.25
E)   −0.800

Question 15

Decreasing the focal length of the eyepiece in a compound microscope by 50% changes the magnification by what factor?

Accepted Answer

A)   0.50
B)   1.5
C)   1.7
D)   2.0
E)   4.0

Question 16

Two lenses, the first with focal length 10.0 cm and the second with focal length −12.5 cm, are separated by 20.0 cm. An object of height 2.40 cm is placed 15.0 cm in front of the first lens. What is the size of the final image?

Accepted Answer

A)   2.40 cm
B)   4.80 cm
C)   12.4 cm
D)   24.0 cm
E)   0.96 cm

Question 17

A simple magnifier of refractive power 15.0 D is used to observe a beetle on a student's desk. Assume that the magnifier is held close to the student's eye. If the image of the beetle is formed at her near point of 25 cm, what is the angular magnification?

Accepted Answer

A)   4.00
B)   3.75
C)   5.95
D)   1.50
E)   4.75

Question 18

Two converging lenses, the first with focal length 40 cm and the second with focal length 331/3 cm, are separated by 10.0 cm. An object of height 6.0 cm is placed 20.0 cm in front of the first lens. Where is the final image formed?

Accepted Answer

A)   10 cm before the first lens
B)   50 cm before the first lens
C)   50 cm after the second lens
D)   100 cm after the second lens
E)   331/3 cm after the second lens

Question 19

An astronomical telescope has a magnifying power of 200 when operated with a 3.50 cm focal length eyepiece. What is the focal length of the objective of this telescope?

Accepted Answer

A)   204 cm
B)   196 cm
C)   700 cm
D)   57.0 cm
E)   30.0 cm

Question 20

Two converging lenses, the first with focal length 10.0 cm and the second with focal length 20.0 cm, are separated by 40.0 cm. An object, 3.00 cm in height, is placed 30.0 cm in front of the first lens. Where is the image formed by the first lens?

Accepted Answer

A)   7.50 cm after the first lens
B)   7.50 cm after the second lens
C)   15.0 cm after the first lens
D)   15.0 cm after the second lens
E)   55.0 cm after the second lens

Exam 24: Optical Instruments