Question 1

Your near point is 25.0 cm, and you're using a 50-diopter lens as a simple magnifier. What magnification do you obtain?

Accepted Answer

A)  12.5 
B)  2 
C)  50 
D)  10 
E)  15.6

Question 2

Half-round slabs of glass or plastic are often used to trace rays. Pins are placed at points P and Q. For an observer to see the images of the pins in line, she should place her eye at point

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  4 
E)  5

Question 3

A stamp collector with a normal near point (25 cm) needs a magnifying power of 10 to examine her stamps. If one of the stamps is 2.0 cm wide, what is the angle (in degrees) subtended by the stamp when it is viewed through her magnifier?

Accepted Answer

A)  23º 
B)  46º 
C)  0.80º 
D)  4.6º 
E)  1.6º

Question 4

How much must the focal length of an eye change when an object, originally at 4.00 m, is brought to 40.0 cm from the eye?

Accepted Answer

A)  0.13 cm 
B)  2.48 cm 
C)  2.35 cm 
D)  2.50 cm 
E)  0.19 cm

Question 5

A cat is watching a goldfish in a spherical fishbowl of radius 15.0 cm. The goldfish is 5.00 cm from the side of the bowl nearest the cat. How far from the side of the bowl does the fish appear to be to the cat? (For water, n = 1.33.)

Accepted Answer

A)  7.5 cm 
B)  4.5 cm 
C)  4.1 cm 
D)  3.5 cm 
E)  2.5 cm

Question 6

Two plane mirrors are arranged so that the reflecting surfaces face each other and are parallel. The mirrors are located at x =  2 m and x = 2 m. An object is located at
X = 1 m. The second image from the left mirror is located at

Accepted Answer

A)  -4 m 
B)  -5 m 
C)  -6 m 
D)  -8 m 
E)  None of the above.

Question 7

An object is located 3 cm in front of a converging lens of focal length 2 cm. A diverging lens of -6 cm focal length is placed 3 cm on the other side of the converging lens. What is the final image distance with respect to the diverging lens?

Accepted Answer

A)  $\infty$ 
B)  2 cm 
C)  -2 cm 
D)  6 cm 
E)  -6 cm

Question 8

An object is placed 20 cm to the left of a converging lens with a focal length of 8 cm. A second converging lens of focal length 12 cm is placed to the right of the first lens. If the final image of the combined lens system is virtual and 15 cm from the second lens, then calculate the distance between the two lenses.

Accepted Answer

A)  73.3 cm 
B)  46.7 cm 
C)  60.0 cm 
D)  6.63 cm 
E)  20.0 cm

Question 9

Your microscope has an objective lens of focal length 1.50 cm and an eyepiece of focal length 2.50 cm separated by 20.0 cm. What is the magnifying power if your near point is 25.0 cm?

Accepted Answer

A)  150 
B)  -150 
C)  200 
D)  -75 
E)  None of these is correct.

Question 10

How much must the focal length of an eye change when an object, originally at 5.00 m, is brought to 30.0 cm from the eye?

Accepted Answer

A)  0.13 cm 
B)  2.31 cm 
C)  2.35 cm 
D)  0.18 cm 
E)  2.49 cm

Question 11

A circular coin is 33.3 cm from a concave spherical mirror. (Assume the coin is on the optical axis.) The image of the coin is produced 10.0 cm from the mirror and on the same side as its real position. If the coin is moved to a position 23.3 cm from the mirror, calculate how far from the mirror the new image is:

Accepted Answer

A)  13.7 cm 
B)  10.0 cm 
C)  15.1 cm 
D)  8.35 cm 
E)  11.5 cm

Question 12

Which of the following statements is false?

Accepted Answer

A)  The image produced by a diverging lens is always virtual, upright, and reduced in size. 
B)  The image produced by a converging lens can be virtual, upright, and magnified in size. 
C)  The image produced by a converging lens can never virtual, upright, and reduced in size. 
D)  To produce a real image, an object has to be place further away than the focal point of a converging lens. 
E)  The image produced by a converging lens cannot be real, inverted, and reduced in size.

Question 13

Your nearsighted coach cannot focus clearly on objects more distant than 50 cm from his eye. What power lenses are required for him to follow the flight of a batted ball?

Accepted Answer

A)  50 
B)  -2.0 
C)  0.67 
D)  -0.67 
E)  2.0

Question 14

A short sighted person's range of vision is between 12 cm and 35 cm from the eye. What focal length lens is needed to allow her to see distant objects clearly?

Accepted Answer

A)  35 cm 
B)  -12 cm 
C)  -23 cm 
D)  12 cm 
E)  -35 cm

Question 15

An object placed 7.62 cm from a simple magnifying glass of focal length 10.2 cm is magnified

Accepted Answer

A)  1x 
B)  2x 
C)  3x 
D)  4x 
E)  0.75x

Question 16

An object 2 cm high is placed 20 cm from a thin convex lens that has a focal length of 10 cm. Which of the following statements describes the image formed?

Accepted Answer

A)  It is 2 cm high. 
B)  It is 20 cm from the lens. 
C)  It is inverted. 
D)  It is real. 
E)  All of these are correct.

Question 17

A real object is 42 cm from a negative lens with f = -21 cm. The image is

Accepted Answer

A)  real and 14 cm from the lens. 
B)  real and 42 cm from the lens. 
C)  virtual and 42 cm from the lens. 
D)  virtual and 21 cm from the lens. 
E)  virtual and 14 cm from the lens.

Question 18

Two plane mirrors make an angle of 120° as shown. An object is placed at O. When the eye is placed at E, it will observe images formed at

Accepted Answer

A)  1 and 2 
B)  2 and 3 
C)  3 and 4 
D)  1 and 4 
E)  1 and 3

Question 19

The lens system used in a Galilean telescope or opera glasses consists of a positive lens and a negative lens on the same axis. In the following ray diagrams the focal points of the positive lens are marked F and F' and those of the negative lens are marked f and f'. The points F and f' coincide. A ray of light comes from a distant object, traverses the system, and enters an eye on the right side of the diagram. Which of the ray diagrams is correct?

Accepted Answer

A)   
B)   
C)   
D)   
E)  None of these is correct.

Question 20

For a myopic eye that cannot focus on objects more than 25 cm in front of it, the power in diopters of the lens needed for distinct distant vision is

Accepted Answer

A)  +25 diopters 
B)  +4.0 diopters 
C)  -4.0 diopters 
D)  -2.5 diopters 
E)  None of these is correct.

Exam 12: Optical Images