Deck 24: Optical Instruments

Question 1

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. What are the size and orientation of the final image?

A) 6.0 cm, upright
B) 6.0 cm, inverted
C) 24 cm, upright
D) 24 cm, inverted
E) 1.5 cm, inverted

Answer 1

24 cm, inverted

Question 2

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. What is the height of the final image?

A) 3.00 cm
B) 1.50 cm
C) 6.00 cm
D) 12.0 cm
E) 24.0 cm

Answer 2

6.00 cm

Question 3

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?

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

Answer 3

−0.800

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. What is the height of the final image?

A) 4.0 cm
B) 2.0 cm
C) 8.0 cm
D) 9.3 cm
E) 1.0 cm

Question 5

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?

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 6

A lens of focal length 1500 mm is used to project an image of the Sun onto a screen. If the Sun subtends an angle of 0.50° in the sky, what is the diameter of the image on the screen?

A) 60 mm
B) 30 mm
C) 26 mm
D) 6.5 mm
E) 13 mm

Question 7

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. Which of the following characteristics does the final image have?

A) real and upright
B) real and inverted
C) virtual and upright
D) virtual and inverted
E) none of these choices are correct

Question 8

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?

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

Question 9

Two lenses with refractive powers of 10 D and 15 D are placed in contact. What is the refractive power of the combination?

A) 15 D
B) 25 D
C) 0.67 D
D) 5.0 D
E) 1.5 D

Question 10

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. Where is the final image?

A) 20.0 cm after the second lens
B) 12.5 cm after the second lens
C) 5.60 cm after the second lens
D) 50.0 cm after the second lens
E) 100 cm after the second lens

Question 11

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 final image?

A) 20 cm after the second lens
B) 20 cm before the second lens
C) 10 cm after the second lens
D) 10 cm before the second lens
E) 50 cm after the second lens

Question 12

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?

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 13

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?

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

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, where is the final image formed?

A) 10.0 cm before the first lens
B) 25.0 cm before the second lens
C) 25.0 cm after the second lens
D) 50.0 cm after the second lens
E) 100 cm after the second lens

Question 15

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. Which of the following characteristics does the final image have?

A) real and upright
B) real and inverted
C) virtual and upright
D) virtual and inverted
E) none of these choices are correct

Question 16

The lens of a slide projector has a focal length of 10.0 cm. It is used to project the image of a 35 mm slide (24 mm × 36 mm) onto a square screen located 6.0 m away. Of the following screen widths, which is the smallest that would allow the entire image to fit?

A) 5.1 m
B) 4.4 m
C) 2.2 m
D) 1.1 m
E) 0.88 m

Question 17

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 final image formed?

A) 11.1 cm after the second lens
B) 100 cm after the second lens
C) 45.0 cm after the second lens
D) 5.00 cm after the second lens
E) 5.00 cm before the second lens

Question 18

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?

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

Question 19

A 50.0 mm lens is used to take a picture of an object 1.30 m tall located 4.00 m away. What is the height of the image on the film?

A) 21.0 mm
B) 16.5 mm
C) 12.0 mm
D) 10.5 mm
E) 9.20 mm

Question 20

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. Which of the following characteristics does the final image have?

A) real and upright
B) real and inverted
C) virtual and upright
D) virtual and inverted
E) virtual and diminished in size

Question 21

A concave mirror has a radius of 2.0 m. What is the refractive power of a lens of the same focal length as the mirror?

A) 0.50 D
B) 1.0 D
C) 2.0 D
D) 0.75 D
E) −0.50 D

Question 22

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?

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

Question 23

For maximum angular magnification in a compound microscope, the objective focal length (f_o) and the eyepiece focal length (f_e) should be chosen so that

A) f_o and f_e are both the largest available.
B) f_o and f_e are both the smallest available.
C) f_o is the smallest available; f_e is the largest available.
D) f_o is the largest available; f_e is the smallest available.
E) f_o and f_e are about the same.

Question 24

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.

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

Question 25

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?

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

Question 26

To get the same exposure on the film when the aperture diameter of a camera lens is doubled, what change should be made in the shutter speed?

A) It should be doubled.
B) It should be halved.
C) It should be quadrupled.
D) It should be quartered.
E) It should be reduced by a factor of 1.414.

Question 27

A farsighted person cannot see clearly closer than 2.0 m. What power contact lenses would correct this near point to 25 cm?

A) 2.0 D
B) 0.5 D
C) −0.5 D
D) 3.5 D
E) −3.5 D

Question 28

A camera with a 50.0 mm lens is designed to focus on objects at distances ranging from 1.00 m to infinity. How far must the lens be able to move, relative to the image sensor plane, to focus over this range?

A) 50.0 mm
B) 52.6 mm
C) 47.4 mm
D) 5.30 mm
E) 2.63 mm

Question 29

A 5.0 cm focal length lens is used as a magnifier. Assuming a near point of 25 cm, about what magnification is attained?

A) 25
B) 10
C) 60
D) 1.2
E) 5

Question 30

Increasing the aperture size on a camera

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 31

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

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

Question 32

Three lenses, each of focal length 90 cm, are placed in contact. What is the focal length of the combination?

A) 27 cm
B) 93 cm
C) 1/30 cm
D) 45 cm
E) 30 cm

Question 33

The loss of accommodation that comes with aging is called

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

Question 34

The refractive power of a lens of focal length 40 cm is

A) 4.0 D.
B) 0.40 D.
C) 2.5 D.
D) −2.5 D.
E) 0.16 D.

Question 35

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.

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

Question 36

A small object has an angular diameter of 0.50°. When viewed through a magnifier, it has an angular diameter of 8.0°. What is the angular magnification in this case?

A) 4.0
B) 8.0
C) 16
D) 32
E) 8.5

Question 37

A lens has a refractive power of −1.50 D. What is its focal length?

A) 150 cm
B) −150 cm
C) 66.7 cm
D) −66.7 cm
E) 8.50 cm

Question 38

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

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.

Question 39

A nearsighted person has a far point of 33 cm. What focal length contact lens would allow her to see in the distance?

A) 33 cm
B) −33 cm
C) 67 cm
D) −67 cm
E) 3.0 m

Question 40

The eye focuses by

A) moving the lens.
B) moving the retina.
C) moving both the lens and the retina.
D) changing the focal length of the lens.
E) changing the index of refraction of the vitreous fluid.

Question 41

An astronomical telescope has a barrel length of 33 cm and an angular magnification of 10. What are the focal lengths of the objective and the eyepiece, respectively?

A) 0.3 m, 3 m
B) 30 cm, 3 cm
C) 20 cm, 13 cm
D) 3 cm, 30 cm

Question 42

Reflecting telescopes may suffer from what kind of aberration(s)?

A) spherical
B) chromatic
C) spherical and chromatic
D) cinematic
E) Brewster and parabolic

Question 43

An astronomical telescope is made with lenses of focal lengths 80.0 cm and 2.00 cm. Two stars in the sky are separated by 0.080°. What angle of separation do they have when viewed in the telescope?

A) 40°
B) 6.4°
C) 3.2°
D) 1.6°
E) 0.080°

Question 44

Which of the following is not necessarily true about the image produced by a pinhole camera?

A) The image is inverted.
B) The image is smaller than the object.
C) The image is real.
D) None of the answer choices are correct.

Question 45

Which statement below best explains why we are able to see details of a distant object more clearly when viewed through a telescope?

A) The image formed by the telescope is larger than the object.
B) The image formed by the telescope subtends a larger angle at the eye than the object does.
C) The intermediate image formed by the objective lens is greatly magnified.
D) Both the objective and eyepiece form real images.

Question 46

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

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

Question 47

A pinhole camera is used to produce an image of a bird that is 3.8 m away. If the size of the bird's image on the screen is 3.0% of the size of the bird, what is the distance from pinhole to screen?

A) 5.7 cm
B) 23 cm
C) 11 cm
D) impossible to determine given the information.

Question 48

How is chromatic aberration corrected in large astronomical reflecting telescopes?

A) a combination of lenses designed to cancel the aberrations
B) use a parabolic mirror instead of a spherical mirror
C) a reflecting telescope has no chromatic aberration
D) change the resolution of the telescope

Question 49

A compound microscope gives a magnification of 200 with an eyepiece of focal length 2.00 cm. If the eyepiece is replaced with an eyepiece of focal length 1.50 cm, what magnification results?

A) 150
B) 133
C) 89
D) 267
E) 300

Question 50

What causes spherical aberration?

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.

Question 51

What causes chromatic aberration?

A) The index of refraction depends on the wavelength.
B) The outer edges of the lens produce a focus at a different point than the central rays.
C) The absorption of light in the glass depends on the wavelength.
D) The coefficient of reflection depends on the wavelength.

Question 52

A TEM is a nonoptical microscope. What does TEM stand for?

A) transverse electron magnifier
B) telescopic emulation machine
C) triple emission magnifier
D) transmission electron microscope
E) none of these answers are correct

Question 53

An astronomical telescope is made with lenses of focal lengths 80.0 and 1.25 cm. What magnifying power does this telescope provide?

A) 10
B) 81
C) 79
D) 64
E) 41

Question 54

A telescope is set up in an introductory physics lab using lenses of focal lengths 10 cm and 50 cm. Since both lenses are the same diameter, it is not immediately clear which one to use as the eyepiece and which to use as the objective. If one uses the lens with a 50 cm focal length as the eyepiece, what power results?

A) 500
B) 5
C) 0.2
D) 0.002
E) one cannot look through the system in this direction

Question 55

The objective of an astronomical telescope has a focal length of 900 mm. The telescope has eyepieces of focal lengths 20 mm, 15 mm, and 10 mm. What is the largest magnification for this telescope?

A) 920
B) 900
C) 880
D) 90
E) 60

Question 56

What kind of lenses are used in a compound microscope?

A) The objective is converging; the eyepiece is diverging.
B) The objective is diverging; the eyepiece is converging.
C) The objective and eyepiece are both diverging.
D) The objective and eyepiece are both converging.

Question 57

An astronomical telescope is made with lenses of focal lengths 80.0 and 2.00 cm. What is the barrel length of this telescope?

A) 80.0 cm
B) 82.0 cm
C) 78.0 cm
D) 105 cm
E) 127 cm

Question 58

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?

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

Question 59

An astronomical telescope has a magnifying power of 100 when using a 2.00 cm focal length eyepiece. How long is the barrel of the telescope?

A) 52.0 cm
B) 100 cm
C) 102 cm
D) 200 cm
E) 202 cm

Question 60

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?

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

Question 61

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, how far is the beetle from the magnifier?

A) 50 cm
B) 9.1 cm
C) 4.2 cm
D) 5.3 cm

Question 62

In a Galilean telescope, the eyepiece is a diverging lens, while the objective lens is a converging lens. What is one advantage of this arrangement over a telescope that uses two converging lenses?

A) The observed image is inverted.
B) The observed image subtends a larger angle than the object.
C) The observed image is upright.
D) The observed image is real.
E) The observed image is virtual.

Question 63

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?

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

Question 64

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?

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

Question 65

The corrective lenses of a person suffering from which of the following vision ailments could be used to start a fire by focusing sunlight?

A) myopia
B) no eyeglass lenses can be used to make a fire
C) astigmatism
D) hyperopia
E) cataracts

Question 66

You use a camera with a lens of focal length 50.0 mm to take a picture of a 2.50 m tall statue located 7.20 m away. If the image height on the film is 18.2 mm, what is the distance from the lens to the film?

A) 5.04 cm
B) need more information
C) 6.32 mm
D) 5.24 cm

Question 67

The pupil of the eye controls

A) the focal length of the eye.
B) the far point.
C) the near point.
D) the amount of light reaching the retina.
E) none of these

Question 68

The image produced on the retina by the lens of the eye, when properly focused, is

A) real and inverted.
B) virtual and inverted.
C) real and upright.
D) virtual and upright.