Question 1

How many electrons surround the nucleus of a neutral atom of iron,the 26th element in the periodic table?

Accepted Answer

A)   26
B)   27
C)   52
D)   25E) All of the above
F) None of the above

Question 2

Which of the following items is considered to be the BEST one to use in a spectrograph to disperse light into its spectrum of colors?

Accepted Answer

A)   a CCD array
B)   a diffraction grating
C)   a glass prism
D)   a two-element achromatic lensE) A) and B)
F) All of the above

Question 3

How many electrons surround the nucleus of a neutral atom of the isotope ¹⁸O of oxygen?

Accepted Answer

A)   18
B)   7
C)   10
D)   8E) All of the above
F) C) and D)

Question 4

The Doppler effect is the change in the wavelength of light caused by the source:

Accepted Answer

A)   being in a high gravitational field.
B)   being embedded in a cloud of dust and gas.
C)   being in an intense magnetic field.
D)   moving with respect to the observer.E) None of the above
F) C) and D)

Question 5

What prevented Ole Rømer from calculating an accurate value for the speed of light from his measurements of the delays in eclipse times of Jupiter's moons?

Accepted Answer

A)   The dimensions of the solar system, particularly the length of 1 AU, were known only very inaccurately.
B)   Telescopes were not good enough at that time to show Jupiter's moons clearly, and accurate timings were not therefore possible.
C)   The distance between Earth's orbit and Jupiter's orbit was unknown.
D)   The clocks available at that time were not sufficiently accurate.E) A) and D)
F) A) and C)

Question 6

How does the angular resolution (sharpness) of the images obtained from radio telescopes using very-long-baseline interferometry (VLBI) compare with the typical angular resolution of optical telescopes?

Accepted Answer

A)   VLBI images are about 10 times less sharp than the best optical images.
B)   VLBI images are much sharper.
C)   VLBI images are much less sharp because of the longer wavelength.
D)   VLBI images have about the same resolution as the best optical images, about 0.2 arc seconds.E) None of the above
F) B) and C)

Question 7

The Balmer series of visible spectral emissions from hydrogen gas arises from transitions in which electrons jump between energy levels:

Accepted Answer

A)   from all levels to the ground state, n = 1.
B)   from higher levels to the second excited level, n = 3.
C)   between adjacent levels (e.g., n = 2 to n = 1, n = 3 to n = 2, n = 4 to n = 3, etc.) .
D)   from higher levels to the first excited level, n = 2.E) None of the above
F) C) and D)

Question 8

If all stars are considered to be perfect blackbodies,then the following relationship should hold regarding the energy flux,or energy emitted per unit area,from stars.

Accepted Answer

A)   All stars of the same mass emit the same energy flux.
B)   All stars of the same temperature emit the same energy flux.
C)   All stars of the same composition (made of exactly the same material)  emit the same energy flux.
D)   All stars of the same size emit the same energy flux.E) B) and C)
F) A) and B)

Question 9

A Newtonian reflecting telescope is constructed using a:

Accepted Answer

A)   concave primary mirror and a flat, diagonal secondary mirror.
B)   concave primary mirror and a concave secondary mirror that reflects light through a hole in the primary mirror.
C)   concave primary mirror and a convex secondary mirror that reflects light through a hole in the primary mirror.
D)   convex primary mirror and a flat, diagonal mirror mounted at 45° to the primary mirror.E) A) and C)
F) A) and D)

Question 10

It is difficult to improve the angular resolution of optical telescopes located on the surface of Earth beyond a certain limit because:

Accepted Answer

A)   large telescopes are always reflecting telescopes, and they suffer from too much chromatic aberration.
B)   spherical mirrors suffer from too much aberration.
C)   star images are distorted more by air turbulence than by the telescope optics.
D)   improvement would require much larger, very expensive telescopes to enhance the inherent telescope.E) A) and B)
F) A) and D)

Question 11

If a continuous spectrum of ultraviolet radiation passes through a tube of cool hydrogen gas,what happens to its spectrum?

Accepted Answer

A)   All the radiation passes unhindered, except the Lyman L
B)   Some of the radiation at all wavelengths is absorbed, reducing the intensity at all wavelengths uniformly.
C)   All the radiation passes through the tube unhindered because the hydrogen gas is cool and cannot absorb energy.
D)   All the radiation passes through the tube unhindered, except at the specific wavelengths of the Lyman series, Lα, Lβ, and so on, which are absorbed by the atoms.E) B) and C)
F) C) and D)

Question 12

Spherical aberration can be corrected or avoided in a reflecting telescope by:

Accepted Answer

A)   grinding the mirror to a more accurate spherical curve.
B)   grinding the mirror to a parabolic shape.
C)   using light of only one color.
D)   grinding the mirror to an elliptical shape.E) A) and B)
F) A) and C)

Question 13

All forms of light have what property in common?

Accepted Answer

A)   All forms of light are electromagnetic radiation.
B)   All forms of light have the same wavelength.
C)   All forms of light are ultrasonic radiation.
D)   All forms of light have wavelengths between 400 nm and 700 nm.E) B) and C)
F) All of the above

Question 14

What is the reason for the fact that a reflecting telescope used at prime focus does NOT suffer from chromatic aberration?

Accepted Answer

A)   The aluminum coating on the mirror absorbs light from all wavelengths, except the one of interest to the astronomer, and this light is focused perfectly.
B)   The light has passed through only one lens.
C)   All wavelengths of light are reflected by the same amount regardless of color.
D)   The lens is so perfectly formed that all colors of light travel through the lens along the same path.E) None of the above
F) A) and B)

Question 15

The chemical makeup of a star's surface is usually inferred by:

Accepted Answer

A)   theoretical methods, considering the evolution of the star.
B)   spectroscopy of the light emitted by the star.
C)   measuring the chemical elements present in the solar wind.
D)   taking a sample of the star's surface with a space probe.E) B) and C)
F) B) and D)

Question 16

Astronomy from space vehicles is particularly useful because the telescope:

Accepted Answer

A)   is in a gravity-free state; the mirror is not distorted by gravitational stress and can therefore produce sharper images.
B)   moves smoothly and without vibration in a constant orbit and can therefore produce sharp photographs.
C)   is above Earth's absorbing and distorting atmosphere and can measure radiation over a very wide wavelength range.
D)   is in a clean, dust-free environment and scattered light is much reduced.E) C) and D)
F) All of the above

Question 17

The star alpha Proxima Centauri,the nearest star beyond the Sun,is 22 km closer to the Sun every second.This motion of alpha Proxima Centauri toward the Sun is an example of:

Accepted Answer

A)   radial velocity.
B)   precession.
C)   elongation.
D)   proper motion.E) A) and B)
F) A) and C)

Question 18

Which substance in Earth's atmosphere is the MAIN absorber of infrared radiation from space?

Accepted Answer

A)   carbon dioxide
B)   water vapor
C)   ozone
D)   methaneE) None of the above
F) A) and B)

Question 19

At what distance from the objective lens in a refracting telescope is the primary image formed-that is,at what distance would you place photographic film if you wanted to take a photograph?

Accepted Answer

A)   its focal length
B)   its diameter
C)   twice its focal length
D)   immediately behind the lens to collect the most lightE) A) and D)
F) C) and D)

Question 20

How does angular resolution for a given diameter of telescope depend on wavelength?

Accepted Answer

A)   Angular resolution worsens as wavelength increases.
B)   Angular resolution may improve or worsen as wavelength increases, depending on other factors such as intensity and spectral range (e.g., optical, infrared, radio) .
C)   Angular resolution improves as wavelength increases.
D)   Angular resolution depends only on the diameter of the telescope and is independent of wavelength.E) C) and D)
F) A) and B)

Exam 3: Light and Telescopes

It is difficult to improve the angular resolution of optical telescopes located on the surface of Earth beyond a certain limit because:

Correct AnswerverifiedShow Answer

The chemical makeup of a star's surface is usually inferred by:

Correct AnswerverifiedShow Answer

Spherical aberration can be corrected or avoided in a reflecting telescope by:

Correct AnswerverifiedShow Answer

The Doppler effect is the change in the wavelength of light caused by the source:

Correct AnswerverifiedShow Answer

How many electrons surround the nucleus of a neutral atom of the isotope ¹⁸O of oxygen?

Correct AnswerverifiedShow Answer

If a continuous spectrum of ultraviolet radiation passes through a tube of cool hydrogen gas,what happens to its spectrum?

Correct AnswerverifiedShow Answer

How does the angular resolution (sharpness) of the images obtained from radio telescopes using very-long-baseline interferometry (VLBI) compare with the typical angular resolution of optical telescopes?

Correct AnswerverifiedShow Answer

Which substance in Earth's atmosphere is the MAIN absorber of infrared radiation from space?

Correct AnswerverifiedShow Answer

What prevented Ole Rømer from calculating an accurate value for the speed of light from his measurements of the delays in eclipse times of Jupiter's moons?

Correct AnswerverifiedShow Answer

A Newtonian reflecting telescope is constructed using a:

Correct AnswerverifiedShow Answer

How does angular resolution for a given diameter of telescope depend on wavelength?

Correct AnswerverifiedShow Answer

How many electrons surround the nucleus of a neutral atom of iron,the 26th element in the periodic table?

Correct AnswerverifiedShow Answer

If all stars are considered to be perfect blackbodies,then the following relationship should hold regarding the energy flux,or energy emitted per unit area,from stars.

Correct AnswerverifiedShow Answer

What is the reason for the fact that a reflecting telescope used at prime focus does NOT suffer from chromatic aberration?

Correct AnswerverifiedShow Answer

All forms of light have what property in common?

Correct AnswerverifiedShow Answer

Astronomy from space vehicles is particularly useful because the telescope:

Correct AnswerverifiedShow Answer

The Balmer series of visible spectral emissions from hydrogen gas arises from transitions in which electrons jump between energy levels:

Correct AnswerverifiedShow Answer

At what distance from the objective lens in a refracting telescope is the primary image formed-that is,at what distance would you place photographic film if you wanted to take a photograph?

Correct AnswerverifiedShow Answer

The star alpha Proxima Centauri,the nearest star beyond the Sun,is 22 km closer to the Sun every second.This motion of alpha Proxima Centauri toward the Sun is an example of:

Correct AnswerverifiedShow Answer

Which of the following items is considered to be the BEST one to use in a spectrograph to disperse light into its spectrum of colors?

Correct AnswerverifiedShow Answer

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