Question 1

Which of the following types of telescope will suffer from chromatic aberration unless very expensive measures are taken to avoid it?

Accepted Answer

A) radio telescope 
B) Cassegrain telescope 
C) reflecting telescope 
D) refracting telescope 
A) radio telescope 
B) Cassegrain telescope 
C) reflecting telescope 
D) refracting telescope D

Question 2

A particular telescope is set up to use the Coudé focus. What arrangement of mirrors is used to bring the light to this focus?

Accepted Answer

A) A concave primary mirror and concave secondary mirror reflect light back through a hole in the primary mirror. 
B) A series of mirrors channel the light to a remote and fixed location. 
C) A concave primary mirror and flat, diagonal secondary mirror are used. 
D) A concave primary mirror and convex secondary mirror reflect light back through a hole in the primary mirror. 
A) A concave primary mirror and concave secondary mirror reflect light back through a hole in the primary mirror. 
B) A series of mirrors channel the light to a remote and fixed location. 
C) A concave primary mirror and flat, diagonal secondary mirror are used. 
D) A concave primary mirror and convex secondary mirror reflect light back through a hole in the primary mirror. B

Question 3

High energy telescopes detect the radiation at the high-energy end of the electromagnetic spectrum, namely:

Accepted Answer

A) radio waves and microwaves. 
B) infrared. 
C) visible. 
D) x rays and gamma rays. 
A) radio waves and microwaves. 
B) infrared. 
C) visible. 
D) x rays and gamma rays. D

Question 4

What is the present angular resolution of the Hubble Space Telescope for visible light?

Accepted Answer

A) 0.001 arcsec 
B) 0.01 arcsec 
C) 1 arcsec 
D) 0.1 arcsec 
A) 0.001 arcsec 
B) 0.01 arcsec 
C) 1 arcsec 
D) 0.1 arcsec

Question 5

In the reflection of a beam of light from a flat surface, the relationship between the angle of incidence i between the perpendicular to the surface and the incident beam and the angle of reflection r between the perpendicular and the reflected beam is:

Accepted Answer

A) r is equal to 2i. 
B) the reflected ray always follows the perpendicular direction from the reflecting surface. 
C) r is equal to i/2. 
D) r is equal to i. 
A) r is equal to 2i. 
B) the reflected ray always follows the perpendicular direction from the reflecting surface. 
C) r is equal to i/2. 
D) r is equal to i.

Question 6

When light passes from air into glass it is refracted. This means that:

Accepted Answer

A) the intensity of the light wave is reduced. 
B) the frequency of the wave increases. 
C) the wave slows down. 
D) the entire wave turns around and returns to the source. 
A) the intensity of the light wave is reduced. 
B) the frequency of the wave increases. 
C) the wave slows down. 
D) the entire wave turns around and returns to the source.

Question 7

Using the combined signals from radio telescopes on opposite sides of Earth, the highest resolution attainable on astronomical images from Earth's surface by Very Long Baseline Array is:

Accepted Answer

A) 1 arcsec. 
B) 0.001 arcsec. 
C) 0.1 arcsec. 
D) 1 arcmin. 
A) 1 arcsec. 
B) 0.001 arcsec. 
C) 0.1 arcsec. 
D) 1 arcmin.

Question 8

The angular resolution attainable with a radio telescope, compared to that attainable with an optical telescope of the same diameter, is significantly inferior because:

Accepted Answer

A) the wavelength of radio waves is larger than that of visible light. 
B) it is difficult to make a reflector for radio waves since these waves penetrate most materials. 
C) Earth's atmosphere disturbs radio waves from space much more than it does visible light. 
D) radio wavelengths are smaller than visible wavelengths, making it difficult to produce a reflector sufficiently smooth to produce images. 
A) the wavelength of radio waves is larger than that of visible light. 
B) it is difficult to make a reflector for radio waves since these waves penetrate most materials. 
C) Earth's atmosphere disturbs radio waves from space much more than it does visible light. 
D) radio wavelengths are smaller than visible wavelengths, making it difficult to produce a reflector sufficiently smooth to produce images.

Question 9

What do adaptive optics actuators do?

Accepted Answer

A) They deform the telescope mirror to compensate for turbulence in the atmosphere. 
B) They deform the telescope mirror to compensate for the mirror's tendency to sag under its own weight. 
C) They add false color to the images. 
D) They compensate for Earth's rotation. 
A) They deform the telescope mirror to compensate for turbulence in the atmosphere. 
B) They deform the telescope mirror to compensate for the mirror's tendency to sag under its own weight. 
C) They add false color to the images. 
D) They compensate for Earth's rotation.

Question 10

A 10-m-diameter radio telescope has worse angular resolution than a 1-m-diameter optical telescope because:

Accepted Answer

A) radio waves have much longer wavelengths than visible light. 
B) optical mirrors suffer from chromatic aberration. 
C) angular resolution gets worse as mirror size increases. 
D) radio waves have much shorter wavelengths than visible light. 
A) radio waves have much longer wavelengths than visible light. 
B) optical mirrors suffer from chromatic aberration. 
C) angular resolution gets worse as mirror size increases. 
D) radio waves have much shorter wavelengths than visible light.

Question 11

Lenses are used in applications like microscopes and telescopes. What does a lens do in these applications?

Accepted Answer

A) Lenses sort out the entering light by color (or wavelength) and absorb the colors not required for the image. 
B) A lens captures all the light emitted by a source and focuses it to form an image. 
C) A lens reduces the chromatic aberration found in light emitted naturally from a source. 
D) Light that would not otherwise form an image enters a lens and has its direction changed so that it focuses to form an image. 
A) Lenses sort out the entering light by color (or wavelength) and absorb the colors not required for the image. 
B) A lens captures all the light emitted by a source and focuses it to form an image. 
C) A lens reduces the chromatic aberration found in light emitted naturally from a source. 
D) Light that would not otherwise form an image enters a lens and has its direction changed so that it focuses to form an image.

Question 12

A spectrograph is usually used in astronomy to measure the:

Accepted Answer

A) variation of the mass of an object as it moves through space. 
B) distribution of light intensity among the various colors. 
C) vibration of Earth following an earthquake. 
D) brightness of light at one specific color. 
A) variation of the mass of an object as it moves through space. 
B) distribution of light intensity among the various colors. 
C) vibration of Earth following an earthquake. 
D) brightness of light at one specific color.

Question 13

The best diffraction gratings have about how many lines per centimeter?

Accepted Answer

A) 100 
B) 1000 
C) 10,000 
D) 100,000 
A) 100 
B) 1000 
C) 10,000 
D) 100,000

Question 14

The primary reason CCDs can more efficiently observe faint stars than photographic plates of film can is:

Accepted Answer

A) the information on CCDs can be stored electronically. 
B) CCDs are much more efficient at recording the light that falls on them. 
C) CCDs are cheaper to build. 
D) CCDs reduce the diffraction-limited angular resolution. 
A) the information on CCDs can be stored electronically. 
B) CCDs are much more efficient at recording the light that falls on them. 
C) CCDs are cheaper to build. 
D) CCDs reduce the diffraction-limited angular resolution.

Question 15

What happens if adjacent pixels in a CCD become so close together that the angular separation between them is smaller than the resolution limit of the telescope being used?

Accepted Answer

A) The electronic signals from these adjacent pixels will really represent a single signal representing the average intensities of this two-pixel region. 
B) The resolution of the picture will improve dramatically. 
C) The CCD can no longer be used on this instrument. 
D) Only the long-wavelength images will remain sharp. 
A) The electronic signals from these adjacent pixels will really represent a single signal representing the average intensities of this two-pixel region. 
B) The resolution of the picture will improve dramatically. 
C) The CCD can no longer be used on this instrument. 
D) Only the long-wavelength images will remain sharp.

Question 16

If the Sun shines on a simple converging lens made of glass, which of the following can you infer?

Accepted Answer

A) Light of all colors converges to precisely the same point. 
B) The red light converges to a point that is slightly closer to the lens than the point to which the blue light converges. 
C) The blue light converges to a point that is slightly closer to the lens than the point to which the red light converges. 
D) The image of the Sun will be distorted, being more red toward the bottom and somewhat green near the top. 
A) Light of all colors converges to precisely the same point. 
B) The red light converges to a point that is slightly closer to the lens than the point to which the blue light converges. 
C) The blue light converges to a point that is slightly closer to the lens than the point to which the red light converges. 
D) The image of the Sun will be distorted, being more red toward the bottom and somewhat green near the top.

Question 17

You are using a telescope with a diameter of 20 cm, and you are observing with light of wavelength 650 nm. You are looking at the word "astronomy" on a distant signboard. What maximum angular spacing (in arcseconds) between adjacent letters will ensure that the entire word can be seen clearly?

Accepted Answer

A) 0.25 arcsec 
B) 0.50 arcsec 
C) 0.75 arcsec 
D) 1.00 arcsec 
A) 0.25 arcsec 
B) 0.50 arcsec 
C) 0.75 arcsec 
D) 1.00 arcsec

Question 18

The resolution in a telescope is best for which segment of the visible spectrum?

Accepted Answer

A) red 
B) green 
C) blue 
D) The resolution is the same all across the visible spectrum. 
A) red 
B) green 
C) blue 
D) The resolution is the same all across the visible spectrum.

Question 19

Which of the following is not a defect or problem that occurs in a refracting telescope?

Accepted Answer

A) opaqueness of the glass lens to certain wavelengths of light 
B) bubbles in the glass lens that scatters light 
C) chromatic aberration, focusing light of different wavelengths to different foci 
D) spherical aberration at the primary reflecting surface 
A) opaqueness of the glass lens to certain wavelengths of light 
B) bubbles in the glass lens that scatters light 
C) chromatic aberration, focusing light of different wavelengths to different foci 
D) spherical aberration at the primary reflecting surface

Question 20

To produce the sharpest images of very distant objects, the best shape for the polished surface of a large astronomical mirror should be:

Accepted Answer

A) elliptical. 
B) spherical. 
C) perfectly flat and smooth. 
D) parabolic. 
A) elliptical. 
B) spherical. 
C) perfectly flat and smooth. 
D) parabolic.

Exam 6: Optics and Telescopes

Which of the following types of telescope will suffer from chromatic aberration unless very expensive measures are taken to avoid it?

A particular telescope is set up to use the Coudé focus. What arrangement of mirrors is used to bring the light to this focus?

High energy telescopes detect the radiation at the high-energy end of the electromagnetic spectrum, namely:

What is the present angular resolution of the Hubble Space Telescope for visible light?

In the reflection of a beam of light from a flat surface, the relationship between the angle of incidence i between the perpendicular to the surface and the incident beam and the angle of reflection r between the perpendicular and the reflected beam is:

When light passes from air into glass it is refracted. This means that:

Using the combined signals from radio telescopes on opposite sides of Earth, the highest resolution attainable on astronomical images from Earth's surface by Very Long Baseline Array is:

The angular resolution attainable with a radio telescope, compared to that attainable with an optical telescope of the same diameter, is significantly inferior because:

What do adaptive optics actuators do?

A 10-m-diameter radio telescope has worse angular resolution than a 1-m-diameter optical telescope because:

Lenses are used in applications like microscopes and telescopes. What does a lens do in these applications?

A spectrograph is usually used in astronomy to measure the:

The best diffraction gratings have about how many lines per centimeter?

The primary reason CCDs can more efficiently observe faint stars than photographic plates of film can is:

What happens if adjacent pixels in a CCD become so close together that the angular separation between them is smaller than the resolution limit of the telescope being used?

If the Sun shines on a simple converging lens made of glass, which of the following can you infer?

You are using a telescope with a diameter of 20 cm, and you are observing with light of wavelength 650 nm. You are looking at the word "astronomy" on a distant signboard. What maximum angular spacing (in arcseconds) between adjacent letters will ensure that the entire word can be seen clearly?

The resolution in a telescope is best for which segment of the visible spectrum?

Which of the following is not a defect or problem that occurs in a refracting telescope?

To produce the sharpest images of very distant objects, the best shape for the polished surface of a large astronomical mirror should be:

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Mercury, Venus, and Mars: Terrestrial, yet Unique

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Asteroids, Comets, and Impacts

Our Star, the Sun

The Nature of the Stars

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Evolution: The Death of Stars

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Galaxies

Quasars and Active Galaxies

Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

The Search for Extraterrestrial Life

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