Question 1

A microscope has an objective lens of focal length 1.40 mm and an eyepiece of focal length 20.00 mm. It is adjusted for minimum eyestrain for persons with a near point of 25.0 cm. A blood sample is placed 1.50 mm from the objective. How far apart are the lenses?

Accepted Answer

A)  20 mm 
B)  21 mm 
C)  23 mm 
D)  41 mm

Question 2

The pupil of a person's eye changes from a diameter of 3.5 mm to 1.5 mm as the illumination is increased. By what factor does the minimum angle of resolution change?

Accepted Answer

A)  0.43 
B)  0.65 
C)  2.0 
D)  2.3

Question 3

A magnifying glass has a focal length of 7.0 cm. What is the angular magnification if the image is viewed by a person having a relaxed eye with the near point of 25 cm?

Accepted Answer

A)  1.6 
B)  2.6 
C)  3.6 
D)  4.6

Question 4

What is the limiting angle of resolution for a lens of radius 2.0 mm when viewing with light having a wavelength of 600 nm?

Accepted Answer

A)  1.3 × 10-4 rad 
B)  1.5 × 10-4 rad 
C)  1.8 × 10-4 rad 
D)  1.5 × 10-7 rad 
E)  1.8 × 10-7 rad

Question 5

Mahmood is farsighted and cannot see objects clearly that are closer to his eye than 80.0 cm. What is the focal length of the contact lenses that will enable him to comfortably see objects at a distance of 25.0 cm from his eyes?

Accepted Answer

A)  +36.4 cm 
B)  -36.4 cm 
C)  -21.2 cm 
D)  +21.2 cm 
E)  +32.5 cm

Question 6

You are given two converging lenses to build a compound microscope. Lens A has focal length 0.50 cm and lens B has focal length of 3.0 cm. Which one of the two lenses would you use for the objective?

Accepted Answer

A)  Lens A, because it has the shorter focal length. 
B)  Lens B, because it has the longer focal length. 
C)  It makes no difference which lens I use for the objective. 
D)  None, because the objective should be a diverging lens.

Question 7

A magnifying glass uses a converging lens with a refractive power of 20 diopters. What is the angular magnification if the image is to be viewed by a relaxed eye with a near point of 25 cm?

Accepted Answer

A)  5.0 
B)  3.0 
C)  4.0 
D)  1.0 
E)  2.0

Question 8

The closest object that a typical young person with normal vision can focus on clearly is closest to

Accepted Answer

A)  1 cm. 
B)  10 cm. 
C)  25 cm. 
D)  50 cm. 
E)  75 cm.

Question 9

The objective lens of a microscope has a focal length of 2.4 mm and the eyepiece has an angular magnification of 15. The object is positioned 0.060 mm beyond the focal point of the objective. The focal point of the eyepiece is positioned at the real image formed by the objective. The near point of the microscope user is at 25 cm. The magnitude of the overall magnification of the microscope is closest to

Accepted Answer

A)  400. 
B)  450. 
C)  500. 
D)  550. 
E)  600.

Question 10

A machinist with normal vision has a near point at 25 cm. This machinist wears +4.25-diopter eyeglasses in order to do very close work. With these eyeglasses, what is the near point of the machinist? Assume that he wears the glasses extremely close to his eyes.

Accepted Answer

A)  12 cm 
B)  10 cm 
C)  7 cm 
D)  15 cm 
E)  17 cm

Question 11

The objective lens and the eyepiece of a microscope have focal lengths of 4.0 mm and 25 mm, respectively. The objective produces a real image 30 times the size of the object, with the final image viewed at infinity. The near point of the microscope user is at 25 cm. What is the distance between the object and the focal point of the objective lens?

Accepted Answer

A)  0.13 mm 
B)  0.18 mm 
C)  0.23 mm 
D)  0.28 mm 
E)  0.33 mm

Question 12

A person's hyperopic (farsighted) eye can focus on objects that are 75 cm away and farther. What power and what focal length contact lenses should be prescribed so this person can see objects 25 cm and farther from the eye?

Accepted Answer

The answer of A person's hyperopic (farsighted) eye can focus...

Question 13

A slide projector needs to focus the image of a 24.0-mm × 36.0-mm slide onto a square screen 1.50 m on each side. You want to fill the screen as completely as possible without any of the image falling beyond the screen. Due to space constraints in the projector, the slide must be placed 10.5 cm from the lens.
(a) What magnification does the projector produce?
(b) How far from the lens should the screen be placed?
(c) What focal length projector lens is needed?

Accepted Answer

The answer of A slide projector needs to focus the...

Question 14

The power of a lens is 4.0 diopters and its diameter is 5.0 cm. What is the focal length of this lens?

Accepted Answer

A)  25 cm 
B)  55 cm 
C)  10 cm 
D)  0.25 cm 
E)  2.5 cm

Question 15

A very delicate sample is placed 0.150 cm from the objective lens of a microscope. The focal length of the objective is 0.140 cm, and that of the eyepiece is 1.0 cm. The near-point distance of the person using the microscope is 25.0 cm. The magnitude of the final magnification of the microscope is closes to

Accepted Answer

A)  375. 
B)  300. 
C)  250. 
D)  125. 
E)  100.

Question 16

A nearsighted person has a far point that is 4.2 m from his eyes. What power contact lenses must he wear to allow him to focus on distant mountains?

Accepted Answer

A)  0.48 diopters 
B)  -0.48 diopters 
C)  -0.36 diopters 
D)  -0.24 diopters 
E)  0.24 diopters

Question 17

Alice is farsighted and cannot see objects clearly that are closer to her eye than 80.0 cm. What is the refractive power of the contact lenses that will enable her to comfortably see objects at a distance of 25.0 cm from her eyes?

Accepted Answer

A)  +2.75 diopters 
B)  -2.75 diopters 
C)  -4.72 diopters 
D)  +4.72 diopters 
E)  +7.00 diopters

Question 18

The two stars in a binary star system have an angular separation of 1.0 × 10-5 rad. If the wavelength of the light from the system is 500 nm, what is the smallest diameter aperture telescope that could just resolve this system to show that it contains two stars?

Accepted Answer

A)  0.50 cm 
B)  0.61 cm 
C)  5.0 cm 
D)  6.1 cm

Question 19

What is the focal length of a contact lens that will allow a person with a near point of 125 cm to read a physics book held 25.0 cm from his eyes?

Accepted Answer

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

Question 20

The focal lengths of the objective lens and the eyepiece in a microscope are 0.29 cm and 2.50 cm, respectively. An object is placed at 0.30 cm from the objective lens and the image of this object is viewed with the eyepiece adjusted for minimum eyestrain for persons with a near point of 25 cm. The magnitude of the final overall magnification of the microscope is closest to

Accepted Answer

A)  100 
B)  200 
C)  300 
D)  410 
E)  500

Exam 19: Optical Instruments