Question 1

Cal is viewing the Moon with his new telescope, using a 10-mm focal length eyepiece. For greater detail, he wishes to double the magnification of his telescope. An eyepiece having which one of the following characteristics will accomplish this for him?

Accepted Answer

A) 40 diopters 
B) 8 mm 
C) 12 mm 
D) 200 diopters 
E) 5 diopters

Question 2

Which one of the following statements is correct?

Accepted Answer

A) The image formed by the objective of a microscope is smaller than the object. 
B) The image formed by the objective lens of a telescope is larger than the object. 
C) The image formed by the eyepiece is real for both a microscope and a telescope. 
D) The image formed by the objective lens of a microscope is larger than the object.

Question 3

A camera with a 20-cm diameter lens is recording images using a filter that allows only light of wavelength 600 nm to pass through. (a)What is the limit on the angular resolution (in microradians)in this case? (b)What is the diameter of the minimum-sized features that could be resolved on Mars with this camera? The distance to Mars at the time is 9.0 × 10⁷ km.

Accepted Answer

The answer of A camera with a 20-cm diameter lens...

Question 4

If the diameter of a radar dish is doubled, what happens to its resolving power assuming that all other factors remain unchanged?

Accepted Answer

A) The resolving power quadruples. 
B) The resolving power doubles. 
C) The resolving power is cut in half. 
D) The resolving power is reduced to one-quarter its original value.

Question 5

The length of a telescope is 2.00 m and the focal length of the objective lens is 2.0 cm. What is the focal length of the eyepiece?

Accepted Answer

A) 200 cm 
B) 202 cm 
C) 101 cm 
D) 2.0 cm 
E) 198 cm

Question 6

A student constructs an astronomical telescope with a magnification of 10. If the telescope has an objective lens of focal length 0.50 m, what is the resulting length of the telescope?

Accepted Answer

A) 53 cm 
B) 55 cm 
C) 60 cm 
D) 75 cm

Question 7

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 8

A nearsighted person cannot see objects beyond 80 cm from his eyes. Which one of the following combinations represents the correct focal length and the refractive power of the contact lenses that will enable him to comfortably see the distant objects clearly?

Accepted Answer

A) +80 cm, +1.3 diopters 
B) -80 cm, +1.3 diopters 
C) +80 cm, -1.3 diopters 
D) -80 cm, -1.3 diopters 
E) -1.3 cm, +1.3 diopters

Question 9

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 10

A farsighted boy has a near point at 2.3 m and requires contact lenses to correct his vision to the normal near point. What is the correct choice of lens power for the contact lenses?

Accepted Answer

A) -0.28 diopters 
B) +0.28 diopters 
C) -3.6 diopters 
D) +3.6 diopters 
E) +1.8 diopters

Question 11

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 12

A person's eye lens is 2.8 cm from the retina, and his near point is at 25 cm. What must be the focal length of his eye lens so that an object at the far point of the eye will focus on the retina?

Accepted Answer

A) -2.8 cm 
B) 2.8 cm 
C) -2.4 cm 
D) 2.4 cm 
E) 2.2 cm

Question 13

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 14

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 15

A camera used for aerial mapping has a lens with a 30-cm diameter maximum aperture and a 42-cm focal length. Light of 550 nm wavelength is used to form the image. Assuming that the resolution of the camera is limited only by diffraction, what is the smallest angle (in milliradians)subtended by an object on the ground that can be resolved by this camera at maximum aperture?

Accepted Answer

A) 1.6 mrad 
B) 2.2 mrad 
C) 3.2 mrad 
D) 4.5 mrad 
E) 6.3 mrad

Question 16

As a treatment for cataracts (a cloudiness of the lens of the eye), the natural lens is removed and a plastic lens is implanted. After this is done a person can see distant objects clearly, but he cannot accommodate to focus on nearby objects. If such a person wanted to read a book at a distance of 25 cm, he would have to wear contact lenses having a diopter power of

Accepted Answer

A) +2.78 diopters 
B) +3.33 diopters 
C) -1.78 diopters 
D) +4.00 diopters 
E) -4.00 diopters

Question 17

Assuming a pupil diameter of 3 mm, what is the angular resolution of the human eye for light at the middle of the visible spectrum (550 nm)?

Accepted Answer

A) 0.8° 
B) 0.2° 
C) 2 mrad 
D) 0.01° 
E) 2°

Question 18

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 19

The focal length of the objective lens of a telescope is 0.20 m and the eyepiece has a focal length of 1.6 m. What is the length of this telescope?

Accepted Answer

A) 8.0 m 
B) 1.4 m 
C) 0.90 m 
D) 1.6 m 
E) 1.8 m

Question 20

You have available lenses of focal lengths 2.0 cm, 4.0 cm, 8.0 cm, and 16.0 cm. If you could use any two of these lenses to build a telescope, what is the maximum magnification you could achieve for comfortable viewing of a planet?

Accepted Answer

A) 2.0 
B) 4.0 
C) 6.0 
D) 8.0

Exam 19: Optical Instruments