Multiple-Choice Questions

1) Which type of telescope has the simplest light path?

A) prime focus reflector

B) single lens refractor

C) achromatic refractor

D) Newtonian reflector

E) Cassegrain reflector

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2) Which type of telescope did Galileo turn skyward in 1610?

A) prime focus reflector

B) single lens refractor

C) achromatic refractor

D) Newtonian reflector

E) Cassegrain reflector

Page Ref: 3.1

3) What problem do refractor telescopes have that reflectors don't?

A) diffraction limited resolution

B) light loss from secondary elements

C) chromatic aberration

D) spherical aberration

E) bad seeing

Page Ref: 3.1

4) The most important advantage of CCDs over film is that

A) they record much more light in a given exposure time.

B) their images do not have to be developed as film does.

C) they record colors better than film can.

D) they can cover larger areas of the sky than film can.

E) their images never fade, as film can.

Page Ref: 3.1

5) The primary purpose of a telescope is to

A) collect a large amount of light and bring it into focus

B) magnify distant objects

C) separate light into its component wavelengths

D) make distant objects appear nearby 

E) measure the brightness of stars very accurately

Page Ref: 3.1

6) A major advantage of a Newtonian reflector over a refractor is

A) its compact size.

B) the elimination of chromatic aberration.

C) there are only two lenses to grind.

D) the central hole in the mirror is smaller.

E) the elimination of the secondary mirror.

Page Ref: 3.1

7) Adding a secondary concave lens of carefully chosen different glass to the primary lens on a refractor allows

A) chromatic aberration to be reduced.

B) x-rays to be focused.

C) effects of atmospheric turbulence to be reduced.

D) greater magnification.

E) more light to be gathered.

Page Ref: 3.1

8) It is diffraction that limits the ________ of a telescope's objective.

A) magnification

B) resolution

C) light grasp

D) wavelengths

E) frequencies

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9) The angular resolution of an 8 inch diameter telescope is  _______ greater than that of a 2 inch diameter telescope. 

A) 2×

B) 4×

C) 8×

D) 9×

E) 16×

Page Ref: 3.2

10) The amount of diffraction and thus the resolution of the scope depends upon

A) the wavelength used and the size of the main telescope objective lens or mirror.

B) the design of the telescope.

C) whether the telescope is a reflector or refractor.

D) the brightness of the object.

E) the size and sensitivity of the CCD chip used for imaging.

Page Ref: 3.2

11) What is the resolution of a telescope?

A) its ability to see very faint objects

B) its ability to distinguish two adjacent objects close together in the sky

C) its ability to make distant objects appear much closer to us

D) its ability to separate light into its component colors for analysis

E) its ability to focus more than just visible light for imaging

Page Ref: 3.2

12) Compared to a 5 inch prime focus reflector, a 5 inch Newtonian reflector will

A) have more light gathering power.

B) have the same light gathering power.

C) be easier to build.

D) will have more chromatic aberration.

E) will have a larger hole in the center of its mirror.

Page Ref: 3.2

13) What is the light-gathering power  of an 8 inch telescope compared to a 4 inch telescope?

A) 2× better

B) 4× better

C) 8× better

D) 16× better

E) 32× better

Page Ref: 3.2

14) Green light has a shorter wavelength than orange light.  In a 5 inch telescope, green light will

A) provide better angular resolution than orange light.

B) come to the same exact focus as orange light.

C) provide worse angular resolution than orange light.

D) allow dimmer stars to be observed.

E) reduce the effects of atmospheric turbulence.

Page Ref: 3.2

15) What problem does adaptive optics correct?

A) defects in the optics of the telescope, such as the original Hubble mirror

B) the opacity of the earth's atmosphere to some wavelengths of light

C) the light pollution of urban areas

D) turbulence in the earth's atmosphere which creates twinkling

E) chromatic aberration due to use of only a single lens objective

Page Ref: 3.3

16) What is true of radio telescopes?

A) They have poorer angular resolution than a refractor.

B) They have better angular resolution than a reflector.

C) They are the smallest, most compact telescopes.

D) They can only be used above the atmosphere.

E) They are most sensitive to the opacity of the ozone layer.  

Page Ref: 3.4

17) The Arecibo radio telescope is laid out like which optical telescope design?

A) prime focus reflector

B) Newtonian reflector

C) Cassegrain reflector

D) Coude reflector

E) grazing incidence reflector

Page Ref: 3.4

18) In astronomy, an interferometer can be used to

A) yield better seeing conditions with optical telescopes

B) decrease the effects of light pollution in getting darker sky backgrounds

C) improve the angular resolution of radio telescopes

D) increase the sensitivity of infrared telescopes to longer wavelengths

E) speed up the processing of CCD images

Page Ref: 3.4

19) Compared to optical telescopes, radio telescopes are built large because

A) they're less expensive to make than optical telescopes.

B) radio photons don't carry much energy.

C) atmospheric turbulance is more of a problem.

D) radio sources are harder to find.

E) radio waves are absorbed by the atmosphere.

Page Ref: 3.4

20) One advantage of the Hubble Space telescope over ground based ones is that

A) it is larger than any Earth-based scopes.

B) it can better focus x-ray images.

C) it can make better observations of the ozone layer.

D) its adaptive optics controls atmospheric blurring better.

E) in orbit, it can operate close to its diffraction limit at visible wavelengths.

Page Ref: 3.3

21) The design of modern x-ray telescopes depends on

A) lenses made of germanium.

B) the prime focus design, with mirrors made of iron.

C) grazing incidence optics.

D) achromatic lenses to keep the x-rays in focus

E) the Cassegrain design, with mirrors made of lead.

Page Ref: 3.5

22) Which of the following is currently supplying high resolution x-ray images from space?


B) Charndra

C) Einstein



Page Ref: 3.5