Deck 27: Magnetic Field and Magnetic Forces

Question 1

Thin lenses: A convex lens has a focal length f. An object is placed at a distance between f and 2f on a line perpendicular to the center of the lens. The image formed is located at what distance from the lens?

A) 2f
B) between f and 2f
C) f
D) between the lens and f
E) farther than 2f

Answer 1

farther than 2f

Question 2

Thin lenses: Which statements are true about a VIRTUAL image? (There may be more than one correct choice.)

A) Its location can be calculated, but it cannot be viewed directly by your eye without using auxiliary lenses.
B) It cannot be photographed.
C) It cannot be viewed on a screen.
D) A plane mirror always forms a virtual image.
E) A concave lens always forms a virtual image.

Answer 2

It cannot be viewed on a screen.
A plane mirror always forms a virtual image.
A concave lens always forms a virtual image.

Question 3

Refracting telescope: A simple refracting telescope provides large magnification by employing

A) a short focal length objective and a short focal length eyepiece.
B) a short focal length objective and a long focal length eyepiece.
C) a long focal length objective and a short focal length eyepiece.
D) a long focal length objective and a long focal length eyepiece.

Answer 3

a long focal length objective and a short focal length eyepiece.

Question 4

Snell's law: In the figure, a laser positioned on a ship is used to communicate with a small two-man research submarine resting on the bottom of a lake. The laser is positioned 12 m above the surface of the water, and it strikes the water 20 m from the side of the ship. The water is 76 m deep and has an index of refraction of 1.33. How far horizontally is the submarine from the side of the ship?

A) 84.1 m
B) 64.1 m
C) 104 m
D) 74.1 m
E) 94.1 m

Question 5

Snell's law: Light strikes a 5.0-cm thick sheet of glass at an angle of incidence in air of 50°. The sheet has parallel faces and the glass has an index of refraction 1.50.
(a) What is the angle of refraction in the glass?
(b) After traveling through the glass the light re-emerges into the air. What is the final angle of refraction in air?
(c) As it leaves the glass, by what distance is the path of the ray is displaced from what it was before entering the glass?

Question 6

Snell's law: A tank holds a 1.44-m thick layer of oil that floats on a 0.96-m thick layer of brine. Both liquids are clear and do not intermix. Point O is at the bottom of the tank, on a vertical axis. The indices of refraction of the oil and the brine are 1.40 and 1.52, respectively. A ray originating at O crosses the brine-oil interface at a point 0.60 m from the axis. The ray continues and emerges into the air above the oil. What is the angle that the ray in the air makes with the vertical?

A) 48°
B) 51°
C) 54°
D) 57°
E) 60°

Question 7

Snell's law: Light in air is initially traveling parallel to the face AC of an equilateral triangular prism, as shown in the figure. The prism is made of glass with an index of refraction of 1.52. If the light does not strike the face AC, what is the angle between the ray as it leaves the prism at face BC and the normal in air at that face?

A) 83°
B) 19°
C) 59°
D) 27°
E) 55°

Question 8

Plane mirrors: As you walk away from a vertical plane mirror, your image in the mirror

A) is always the same height.
B) may or may not decrease in height, depending on where the observer is positioned.
C) is always a real image, no matter how far you are from the mirror.
D) changes from being a virtual image to a real image as you pass the focal point.
E) decreases in height.

Question 9

Compound microscope: Which one of the following is a characteristic of a compound microscope?

A) The objective is a diverging lens.
B) The eyepiece is a diverging lens.
C) The final image is real.
D) The image formed by the objective is virtual.
E) The image formed by the objective is real.

Question 10

Snell's law: A ray of light goes from one transparent material into another, as shown in the figure. What can you conclude about the indices of refraction of these two materials?

A) n₁ ≥ n₂
B) n₁ > n₂
C) n₁ = n₂
D) n₂ ≥ n₁
E) n₂ > n₁

Question 11

Thin lenses: A convex lens has focal length f. If an object is located extremely far from the lens (at infinity), the image formed is located what distance from the lens?

A) infinity
B) 2f
C) between f and 2f
D) f
E) between the lens and f

Question 12

Snell's law: An oil layer that is 5.0 cm thick is spread smoothly and evenly over the surface of water on a windless day. What is the angle of refraction in the water for a ray of light that has an angle of incidence of 45° as it enters the oil from the air above? (The index of refraction for the oil is 1.15, and for water it is 1.33.)

A) 27°
B) 32°
C) 36°
D) 39°
E) 52°

Question 13

Thin lenses: An object is placed in front of a lens which forms an image of the object.

A) If the lens is convex, the image cannot be virtual.
B) If the image is real, then it is also inverted.
C) If the image is real, then it is also upright.
D) If the image is virtual, then it is also inverted.
E) If the image is virtual, the lens must be a diverging lens.

Question 14

Index of refraction: When light goes from one material into another material having a HIGHER index of refraction,

A) its speed, wavelength, and frequency all decrease.
B) its speed and wavelength decrease, but its frequency stays the same.
C) its speed decreases but its wavelength and frequency both increase.
D) its speed decreases but its frequency and wavelength stay the same.
E) its speed increases, its wavelength decreases, and its frequency stays the same.

Question 15

Spherical mirrors: Suppose you place your face in front of a concave mirror. Which one of the following statements is correct?

A) If you position yourself between the center of curvature and the focal point of the mirror, you will not be able to see a sharp image of your face.
B) No matter where you place yourself, a real image will be formed.
C) Your image will always be inverted.
D) Your image will be diminished in size.
E) None of these statements is true.

Question 16

Polarization: Which one of the following is an accurate statement about light?

A) When light strikes a surface at Brewster's angle, the reflected and transmitted light are both 100% polarized.
B) When light strikes a surface at Brewster's angle, it is completely reflected at the surface.
C) When light strikes a surface at Brewster's angle, only the reflected light is 100% polarized.
D) When light strikes a surface at the critical angle, only the reflected light is 100% polarized.
E) When light strikes a surface at the critical angle, all the light passes through the surface.

Question 17

Thin lenses: A convex lens has a focal length f. An object is placed between infinity and 2f from the lens along a line perpendicular to the center of the lens. The image is located at what distance from the lens?

A) farther than 2f
B) 2f
C) between f and 2f
D) f
E) between the lens and f

Question 18

Total internal reflection: The speed of light in a material is What is the critical angle of a light ray at the interface between the material and a vacuum?

A) 30°
B) 21°
C) 24°
D) 27°

Question 19

Total internal reflection: A ray of light strikes a boundary between two transparent materials, and there is no transmitted ray, as shown in the figure. What can you conclude about the indices of refraction of these two materials?

A) n₁ ≥ n₂
B) n₁ > n₂
C) n₁ = n₂
D) n₂ ≥ n₁
E) n₂ > n₁

Question 20

Snell's law: A ray of light passes from glass into a liquid, as shown in the figure. What is the speed of the light in the liquid? (c = 3.00 × 10⁸ m/s)

Question 21

Plane mirrors: How far are you from your image when you stand 0.750 m in front of a vertical plane mirror?

A) 0.375 m
B) 0.750 m
C) 1.50 m
D) 3.00 m

Question 22

Total internal reflection: A tank holds a 1.44-m thick layer of oil that floats on a 0.96-m thick layer of brine. Both liquids are clear and do not intermix. Point O is at the bottom of the tank, on a vertical axis. The indices of refraction of the oil and the brine are 1.40 and 1.52, respectively. A ray originating at O reaches the brine-oil interface at the critical angle. What is the distance of this point from the axis?

A) 1.5 m
B) 1.7 m
C) 1.9 m
D) 2.1 m
E) 2.3 m

Question 23

Polarization: In the figure, the orientation of the transmission axis for each of three polarizing sheets is labeled relative to the vertical direction. A beam of light, polarized in the vertical direction, is incident on the first polarized with an intensity of 1000 W/m². What is the intensity of the beam after it has passed through the three polarizing sheets when θ₁ = 30°, θ₂ = 30° and θ₃ =60°?

A) 141 W/m²
B) 316 W/m²
C) 433 W/m²
D) 563 W/m²
E) 188 W/m²

Question 24

Total internal reflection: A glass plate whose index of refraction is 1.56 is immersed in a liquid. The surface of the glass is inclined at an angle of 42.0° with the vertical. A horizontal ray in the glass is incident on the interface. When the liquid is a certain alcohol, the incident ray arrives at the interface at the critical angle. What is the index of refraction of the alcohol?

A) 1.04
B) 1.02
C) 1.00
D) 0.984
E) 1.06

Question 25

Total internal reflection: The critical angle in air for a particular type of glass is 39.0°. What is the speed of light in this class glass? (c = 3.00 × 10⁸ m/s)

A) 1.97 × 10⁸ m/s
B) 1.94 × 10⁸ m/s
C) 1.91 × 10⁸ m/s
D) 1.89 × 10⁸ m/s
E) 2.00 × 10⁸ m/s

Question 26

Total internal reflection: An optical fiber made of glass with an index of refraction 1.50 is coated with a plastic with index of refraction 1.30. What is the critical angle of this fiber at the glass-plastic interface?

A) 90.0°
B) 41.8°
C) 60.1°
D) 50.2°
E) 61.1°

Question 27

Spherical mirrors: A concave spherical mirror with a radius of 20 cm creates a real image 30 cm from the mirror. How far is the object from the mirror?

A) 50 cm
B) 20 cm
C) 15 cm
D) 7.5 cm
E) 5.0 cm

Question 28

Spherical mirrors: A convex spherical mirror with a focal length of magnitude 25 cm has a 4.0-cm tall flower placed 100 cm in front of it. What is the height of the image of the flower?

A) 0.80 cm
B) 20 cm
C) 4.0 cm
D) 1.6 cm
E) 8.0 cm

Question 29

Spherical mirrors: The spherical side mirror on a car is convex and has a radius of curvature of 25 cm. Another car is following, 20 m behind the mirror. If the height of the car is 1.6 m, how tall is its image?

A) 5.0 cm
B) 2.0 cm
C) 4.0 cm
D) 3.0 cm
E) 0.99 cm

Question 30

Spherical mirrors: A man's face is 30 cm in front of a concave spherical shaving mirror. If the image is erect and 1.5 times as large as his face, what is the radius of curvature of the mirror?

A) 40 cm
B) 60 cm
C) 100 cm
D) 140 cm
E) 180 cm

Question 31

Dispersion: Light consisting of a mixture of red and blue light enters a 40°, 70°, 70° prism along a line parallel to the side opposite the 40° vertex. The index of refraction of the prism material for blue light is 1.530, and for red light it is 1.525. What is the angle between the two emerging beams of light?

A) 0.5°
B) 0.9°
C) 0.1°
D) 0.3°
E) 0.7°

Question 32

Spherical mirrors: An object 4.0 cm in height is placed 8.0 cm in front of a concave spherical mirror with a focal length of 10.0 cm. What is the position of its image in relation to the mirror, and what are the characteristics of the image?

A) 40.0 cm on the other side of mirror, real, 6.0 times bigger
B) 10.0 cm on the other side of mirror, virtual, 10.0 times bigger
C) 18.0 cm on the same side of mirror, virtual, 2.25 times bigger
D) 10.0 cm on the same side of mirror, real, 6.0 times bigger
E) 40.0 cm on the other side of mirror, virtual, 5.0 times bigger

Question 33

Polarization: The following are positioned in sequence: A source of a beam of natural light of intensity I₀; three ideal polarizers A, B, and C; and an observer. Polarizer axis angles are measured clockwise from the vertical, from the perspective of the observer. The axis angle of polarizer A is set at 0° (vertical), and the axis angle of polarizer C is set at 50°. Polarizer B is set so that the beam intensity is zero at the observer. Which of the following pairs of angles are possible axis angle settings of polarizer B?

A) 40° and 90°
B) 40° and 130°
C) 40° and 140°
D) 90° and 130°
E) 90° and 140°

Question 34

Total internal reflection: An optic fiber is made of clear plastic with index of refraction of 1.50, surrounded by air. For what angles of incidence θ will light remain within the plastic fiber?

A) θ ≥ 21.1°
B) θ < 38.3°
C) θ > 38.3°
D) θ < 41.8°
E) θ > 41.8°

Question 35

Dispersion: A ray of light consisting of blue light (wavelength 480 nm) and red light (wavelength 670 nm) is incident on a thick piece of glass at 80°. What is the angular separation between the refracted red and refracted blue beams while they are in the glass? (The respective indices of refraction for the blue light and the red light are 1.4636 and 1.4561.)

A) 0.27°
B) 0.33°
C) 0.36°
D) 0.46°
E) 0.54°

Question 36

Dispersion: A beam of light of two different wavelengths enters a pane of glass 3.00 mm thick at an angle of incidence of 56°. The indices of refraction for the two different colors are 1.514 and 1.528. Because of dispersion, the colored beams, although parallel, are separated by a small distance. How far apart are they?

A) 0.057 mm
B) 0.0083 mm
C) 0.025 mm
D) 0.014 mm
E) 0.0062 mm

Question 37

Total internal reflection: What is the critical angle for light traveling from crown glass (n = 1.52) into water (n = 1.33)?

A) 42°
B) 48°
C) 53°
D) 57°
E) 61°

Question 38

Total internal reflection: A ray of light traveling in air strikes the surface of a certain plastic slab at 63.0° with respect to the normal in air. It travels in the plastic slab at a 30.6° angle with respect to the normal. Find the critical angle for the plastic in air.

Question 39

Polarization: The critical angle for an air-glass interface is 29.6°. When a light ray in air is incident on the interface, the reflected ray is 100% polarized. What is the angle of refraction of that ray?

A) 26.3°
B) 25.7°
C) 25.1°
D) 24.5°
E) 23.9°

Question 40

Spherical mirrors: An object is 12 cm in front of a concave spherical mirror, and the image is 3.0 cm in front of the mirror. What is the focal length of the mirror?

A) 0.25 cm
B) 15 cm
C) 4.0 cm
D) 2.4 cm
E) 1.3 cm

Question 41

Refraction at a curved surface: The left-hand end of a glass rod is ground to a spherical surface. The glass has index of refraction 1.50. A small object 4.00 mm tall is placed on the axis of the rod, 37.0 cm to the left of the vertex of the spherical surface. The image is formed in the rod, 50.0 cm to the right of the vertex.
(a) What is the magnitude of the radius of curvature of the spherical surface at the end of the rod?
(b) What is the height of the image?

Question 42

Thin lenses: An object 1.80 cm tall is placed 100 cm in front of a diverging lens having a focal length of magnitude 25 cm. A converging lens with a focal length of magnitude 33.33 cm is placed 30 cm past the first lens. What is the lateral magnification of this system of lenses?

A) 2.5
B) -2.5
C) -0.40
D) 1.0
E) 0.40

Question 43

Thin lenses: In the figure, the image is viewed on a screen and is 13.5 mm tall. What is the focal length of the lens?

A) +14.6 cm
B) -14.6 cm
C) +20.4 cm
D) -89.3 cm
E) +124 cm

Question 44

Thin lenses: A 4.0-cm tall object is placed 50.0 cm from a diverging lens having a focal length of magnitude 25.0 cm. What are the nature and location of the image? The image is

A) real, 4.0 cm tall, and 20 cm from the lens on the side opposite the object.
B) virtual, 4.0 cm tall, and 20 cm from the lens on the side opposite the object.
C) virtual, 2.0 cm tall, and 10 cm from the lens on the side opposite the object.
D) virtual, 1.3 cm tall, and 16.7 cm from the lens on the same side of the object.
E) real, 1.3 cm tall, and 16.7 cm from the lens on the same side of the object.

Question 45

Spherical mirrors: The image of a plant is 4.0 cm from a concave spherical mirror having a radius of curvature of 10 cm. Where is the plant relative to the mirror?

A) 2.2 cm in front of the mirror
B) 4.4 cm in front of the mirror
C) 9.0 cm in front of the mirror
D) 1.0 cm in front of the mirror
E) 20 cm in front of the mirror

Question 46

Refraction at a curved surface: A fisherman in a stream 39 cm deep looks downward into the water and sees a rock on the stream bed. How deep does the stream appear to the fisherman? The index of refraction of the water is 1.33.

A) 29 cm
B) 52 cm
C) 33 cm
D) 45 cm

Question 47

Thin lenses: An object is placed 10 cm from a convex lens of focal length 20 cm. What is the lateral magnification of the object?

A) 0.50
B) 1.0
C) 1.5
D) 2.0
E) 2.5

Question 48

Thin lenses: It is desired to project the image of an object four times its actual size using a lens of focal length 20 cm. How far from the lens should the object be placed?

A) 100 cm
B) 80 cm
C) 4.0 cm
D) 25 cm
E) 5.0 cm

Question 49

Refraction at a curved surface: A fish appears to be 2.00 m below the surface of a pond when viewed almost directly above by a fisherman. What is the actual depth of the fish? (n_water = 1.33)

A) 2.66 m
B) 0.67 m
C) 1.5 m
D) 0.38 m

Question 50

Thin lenses: A 4.0-cm tall object is placed 60 cm away from a converging lens of focal length 30 cm. What are the nature and location of the image? The image is

A) real, 2.5 cm tall, and 30 cm from the lens on the same side as the object.
B) virtual, 2.5 cm tall, and 30 cm from the lens on the side opposite the object.
C) virtual, 2.0 cm tall, and 15 cm from the lens on the side opposite the object.
D) virtual, 4.0 cm tall, and 60 cm from the lens on the same side as the object.
E) real, 4.0 cm tall, and 60 cm from the lens on the side opposite the object.

Question 51

Thin lenses: An object 1.25 cm tall is placed 100 cm in front of a convex lens with a focal length of magnitude 50 cm. A concave lens with a focal length of magnitude 20 cm is placed 90 cm beyond the first lens. Where is the final image located?

A) 10 cm in front of the second lens
B) 20 cm past the second lens
C) 17 cm past the second lens
D) 10 cm past the second lens
E) 20 cm in front of the second lens

Question 52

Refraction at a curved surface: A goldfish bowl is spherical, 8.0 cm in radius. A goldfish is swimming 3.0 cm from the wall of the bowl. Where does the fish appear to be to an observer outside? The index of refraction of water is 1.33. Neglect the effect of the glass wall of the bowl.

A) 3.3 cm inside the bowl
B) 3.9 cm inside the bowl
C) 2.5 cm inside the bowl
D) 3.0 cm inside the bowl
E) 1.7 cm inside the bowl

Question 53

Thin lenses: In the figure, the thin lens forms a real image of the object 94.0 cm from the object. What is the focal length of the lens?

A) 22.0 cm
B) 25.5 cm
C) 27.5 cm
D) 55.8 cm
E) 86.0 cm

Question 54

Spherical mirrors: An object 3.4 mm tall is placed 25 cm from the vertex of a convex spherical mirror. The radius of curvature of the mirror has a magnitude of 52 cm.
(a) How far is the image from the vertex of the mirror?
(b) What is the height of the image?

Question 55

Thin lenses: When an object 1.15 cm tall is placed 12 cm from a lens, the lens produces an upright image of the object that is 5.75 cm tall. What is the focal length of the lens?

A) 24 cm
B) 18 cm
C) 60 cm
D) 15 cm
E) 9.0 cm

Question 56

Thin lenses: An object is placed 100 cm in front of a lens of focal length 20 cm. A second lens is placed 35 cm beyond the first, this second lens having a focal length of 8.0 cm. If the height of the object is 6.0 cm, what is the height of the final image?

A) 1.5 cm
B) 12 cm
C) 9.0 cm
D) 3.0 cm
E) 6.0 cm

Question 57

Thin lenses: A thin converging lens is found to form an image of a distant building 24 cm from the lens. If an insect is now placed 16 cm from this lens, how far FROM THE INSECT will its image be formed?

A) 64 cm
B) 72 cm
C) 32 cm
D) 96 cm
E) 48 cm

Question 58

Thin lenses: An object is placed 100 cm in front of a diverging lens with a focal length of magnitude 25 cm. A converging lens having a focal length of magnitude 33.33 cm is placed 30 cm past the first lens. Where is the final image formed?

A) 30 cm after the second lens
B) 20 cm in front of the first lens
C) 3.0 meters before the second lens
D) 100 cm after the second lens
E) 3.0 cm before the second lens

Question 59

Spherical mirrors: A convex spherical mirror with a radius of 50 cm has a 4.0 cm tall object placed 100 cm in front of it. What is the position of the image relative to the mirror?

A) 20 cm behind the mirror
B) 25 cm behind the mirror
C) 100 cm in front of the mirror
D) 25 cm in front of the mirror
E) 20 cm in front of the mirror

Question 60

Refraction at a curved surface: A swimming pool is filled to a depth of 2.0 m. How deep does the pool appear to be from above the water, which has an index of refraction of 1.33?

A) 1.5 m
B) 1.33 m
C) 2.5 m
D) 3.0 m
E) 4.0 cm

Question 61

Lens-maker's formula: A thin double convex lens is to focus the image of an object onto a screen so that the image is life-sized. The lens surfaces have equal radii of curvature of 112 cm, and the refractive index of the lens material is 1.500.
(a) How far from the lens should the screen be placed?
(b) How far is the screen from the object?

Question 62

Eyes: The near point of a farsighted person's uncorrected eyes is 80 cm. What power contact lens should be used to move the near point to 25 cm from this person's eyes?

A) 2.8 diopters
B) -2.8 diopters
C) -4.0 diopters
D) -4.2 diopters
E) 4.2 diopters

Question 63

Eyes: What is the uncorrected near point of a person who has a near point that is 25 cm from his eyes when he is wearing 3.33-diopter contact lenses?

A) 1.5 m
B) 0.50 m
C) 1.9 m
D) 0.75 m
E) 0.60 m

Question 64

Eyes: A person's eye lens is 2.7 cm away from the retina. This lens has a near point of 25 cm and a far point at infinity.
(a) What must the focal length of this lens be in order for an object placed at the near point of the eye to focus on the retina?
(b) What must the focal length of this lens be in order for an object placed at the far point of the eye to focus on the retina?

Question 65

Camera: A 35-mm camera equipped with a 95 mm focal length lens is used to photograph a tree that is 8.0 m tall. A 32 mm high image of the tree on the film is needed. The required distance, between the tree and the camera lens, to take the photograph is closest to

A) 24 m.
B) 25 m.
C) 26 m.
D) 27 m.
E) 29 m.

Question 66

Lens-maker's formula: In the figure, the radius of curvature of the curved part of the lens is 24.0 cm, and the refractive index of the lens material is 1.750. What is the focal length of the lens?

A) +32.0 cm
B) -32.0 cm
C) -16.0 cm
D) +13.8 cm
E) -13.8 cm

Question 67

Lens-maker's formula: A double-convex thin lens is made of glass with an index of refraction of 1.52. The radii of curvature of the faces of the lens are 60 cm and 72 cm. What is the focal length of the lens?

A) 70 cm
B) 63 cm
C) 75 cm
D) 66 cm
E) 58 cm

Question 68

Eyes: What power contact lens must be used to correct the vision of a nearsighted person whose far point is 40 cm?

A) 2.5 diopters
B) -2.5 diopters
C) -3.6 diopters
D) -4.0 diopters
E) 4.0 diopters

Question 69

Lens-maker's formula: A convex-concave thin lens is made with the radius of curvature of the convex surface being 25.0 cm and the concave surface 45.0 cm. If the glass used has index of refraction 1.500, what is the focal length of this lens?

A) -32.0 cm
B) 32.0 cm
C) 113 cm
D) 67.5 cm
E) -113 cm

Question 70

Thin lenses: An optical system comprises in turn, from left to right: an observer, a lens of focal length +30 cm, an erect object 20 mm high, and a convex mirror of radius 80 cm. The object is between the lens and the mirror, 20 cm from the lens and 50 cm from the mirror. The observer views the image that is formed first by reflection and then by refraction. What is the position of the final image, measured from the mirror?

A) 90 cm
B) 102 cm
C) 114 cm
D) 126 cm
E) 138 cm

Question 71

Camera: A camera lens has a focal length of 50.0 mm and an aperture setting of f/4.00. What is the aperture diameter of this lens?

A) 12.5 mm
B) 10.1 mm
C) 13.6 mm
D) 14.2 mm
E) 15.0 mm

Question 72

Camera: The focal length of a thin lens is 40 mm and its aperture diameter is 10 mm. What is the f-number of this lens?

A) f/4.0
B) f/2.0
C) f/5.6
D) f/0.30
E) f/0.40

Question 73

Eyes: A nearsighted person has her distant vision corrected using a -2.0-diopter eyeglasses. Her uncorrected near point is 15 cm. What is her near point using this lens if the lens is 2.0 cm from the eye?

A) 17 cm
B) 20 cm
C) 13 cm
D) 18 cm
E) 15 cm

Question 74

Lens-maker's formula: A double-concave lens has equal radii of curvature of An object placed from the lens forms a virtual image from the lens. What is the index of refraction of the lens material?

A) 1.90
B) 1.98
C) 1.82
D) 1.77

Question 75

Camera: In a 35.0-mm single lens reflex camera (SLR), the distance from the lens to the film is varied in order to focus on objects at varying distances. Over what distance range must a lens of 55-mm focal length vary if the camera is to be able to focus on objects ranging in distance from infinity down to 0.60 m from the camera?

A) 5.55 mm
B) 4.44 mm
C) 16.7 mm
D) 22.2 mm
E) 7.77 mm

Question 76

Eyes: The near point of a person's uncorrected eyes is 125.0 cm and the far point is at infinity. What is the focal length of a contact lens that will move the near point to 25.0 cm from this person's eyes?

A) -100 cm
B) -31.3 cm
C) 10.2 cm
D) 20.8 cm
E) 31.3 cm

Question 77

Eyes: What is the focal length of the corrective contact lens needed by a nearsighted person whose far point is 60 cm?

A) -60 cm
B) -30 cm
C) +30 cm
D) +60 cm
E) +130 cm

Question 78

Lens-maker's formula: In the figure, the radius of curvature of the curved part of the lens is 35.0 cm, and the refractive index of the lens material is 1.620. What is the focal length of the lens?

A) +56.5 cm
B) -56.5 cm
C) +28.2 cm
D) +21.6 cm
E) -21.6 cm

Question 79

Lens-maker's formula: A lens is made with a focal length of -40 cm using a material with index of refraction 1.50. A second lens is made with the SAME GEOMETRY as the first lens, but using a material having refractive index of 2.00. What is the focal length of the second lens?

A) -40 cm
B) -80 cm
C) -53 cm
D) -20 cm
E) -30 cm

Question 80

Lens-maker's formula: A compound lens is made by joining the plane surfaces of two thin plano-convex lenses of different glasses. The radius of curvature of each convex surface is 80 cm. The indices of refraction of the two glasses are 1.50 and 1.60. What is the focal length of the compound lens?

A) 67 cm
B) 69 cm
C) 71 cm
D) 73 cm
E) 75cm