Chapter 6 Homework

The Chandra X-ray observatory focuses X rays with _____________________ mirrors.

grazing incidence

The twin 10-m Keck telescopes can work together to obtain better angular resolution through a technique known as ____________________.

interferometry

Telescopes operating at this wavelength must be cooled to observe faint astronomical objects. A) visible B) gamma-ray C) extreme infrared D) radio E) X-ray

C) extreme infrared

At which wavelength range is there no current or planned space observatory? A) infrared B) visible C) radio D) gamma-ray E) X-ray

C) radio

In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate? A) X-ray B) visible C) radio D) infrared E) ultraviolet

C) radio

The ________________ of the Hubble Space Telescope is better for shorter (bluer) wavelengths of light than for longer (redder) wavelengths of light.

angular resolution

What do astronomers mean by light pollution? A) Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations. B) Light pollution is another name for sunlight, which makes it impossible to see stars in the daytime. C) Light pollution refers to the lights that must be used inside major observatories and that make it difficult for astronomers' eyes to adapt to darkness. D) Light pollution refers to harmful gases emitted by common street lights. E) Light pollution refers to pollution caused by light industry as opposed to heavy industry.

A) Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations

Which of the following is always true about images captured with X-ray telescopes? A) They are always displayed in false color. B) They are always useful for seeing through things. C) They are always displayed with north pointing upward in the images. D) They are always displayed with the highest possible angular resolution. E) They are always very pretty.

A) They are always displayed in false color.

What is an artificial star? A) a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations B) a satellite orbiting Earth C) the unseen member of a binary star system D) a possible source of dark matter in the universe E) a meteor

A) a point of light in Earth's atmosphere created by a laser for the purpose of monitoring atmospheric fluctuations

Order the following in order of increasing efficiency of detecting photons of visible light. A) eye, photographic film, CCD B) CCD, photographic film, eye C) photographic film, CCD, eye D) CCD, eye, photographic film E) eye, CCD, photographic film

A) eye, photographic film, CCD

The James Webb Space Telescope is designed primarily to observe __________. A) infrared light B) light of all wavelengths C) X-rays D) gamma rays E) visible light

A) infrared light

Which of the following studies is best suited to a timing experiment? A) studying whether a particular star's brightness is steady or variable B) estimating the time since the Big Bang C) determining the age of the solar system D) studying how different stars differ in their chemical compositions E) measuring the rotation rate of a distant star

A) studying whether a particular star's brightness is steady or variable

Which of the following could not be determined by an observation that uses only spectroscopy? A) the size of a distant galaxy B) the speed at which a distant galaxy is moving away from us C) the chemical composition of a distant star D) the rotation rate of a distant star E) the surface temperature of a distant star

A) the size of a distant galaxy

What do we mean by the diffraction limit of a telescope? A) It describes the farthest distance to which the telescope can see. B) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion. C) It describes the maximum exposure time for images captured with the telescope. D) It is the maximum size to which any telescope can be built.

B) It is the best angular resolution the telescope could achieve with perfect optical quality and in the absence of atmospheric distortion.

Which of the following statements about light focusing is not true? A) If you try to look at an image that is not formed at the focal plane, it will be blurry. B) The focal plane of a reflecting telescope is always located within a few inches of the primary mirror. C) In a healthy eye, light is focused on the retina. D) Film should be placed at the focal plane in a camera.

B) The focal plane of a reflecting telescope is always located within a few inches of the primary mirror.

What causes stars to twinkle? A) It is intrinsic to the stars - their brightness varies as they expand and contract. B) bending of light rays by turbulent layers in the atmosphere C) variable absorption by interstellar gas along the line of sight to the star D) the inability of the human eye to see faint objects E) variations in the absorption of the atmosphere

B) bending of light rays by turbulent layers in the atmosphere

In what wavelength range was interferometry first routinely used? A) optical B) radio C) X-ray D) ultraviolet E) infrared

B) radio

Currently, the largest optical telescope mirrors have a diameter of A) 100 m. B) 5 m. C) 10 m. D) 2 m. E) 1 m.

C) 10 m.

What does the technique of interferometry allow? A) It allows two or more telescopes to obtain a total light-collecting area much larger than the total light-collecting area of the individual telescopes. B) It allows us to determine the chemical composition of stars. C) It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes. D) It allows astronomers to make astronomical observations without interference from light pollution. E) It allows the same telescope to make images with both radio waves and visible light.

C) It allows two or more telescopes to obtain the angular resolution of a single telescope much larger than any of the individual telescopes.

What is meant by spectral resolution? A) It is a measure of how close two point sources can be distinguished. B) It is a measure of how much energy an object emits in different parts of the electromagnetic spectrum. C) It is a measure of how close two spectral lines can be distinguished. D) It is the same as angular resolution when applied to telescopes operating at different wavelengths.

C) It is a measure of how close two spectral lines can be distinguished.

Which of the following statements best describes the two principal advantages of telescopes over eyes? A) Telescopes can see farther without image distortion and can record more accurate colors. B) Telescopes can collect far more light with far greater magnification. C) Telescopes can collect far more light with far better angular resolution. D) Telescopes collect more light and are unaffected by twinkling. E) Telescopes have much more magnification and better angular resolution.

C) Telescopes can collect far more light with far better angular resolution.

If our eyes were sensitive only to X rays, the world would appear __________. A) gray, black, and white like a medical X ray B) brighter than normal because X rays carry more energy than visible light photons C) dark because X-ray light does not reach Earth's surface D) green, yellow, and orange, because those are the colors of X rays

C) dark because X-ray light does not reach Earth's surface

Which of the following is not a good reason to place observatories on remote mountain tops? A) to reduce light distortion B) to reduce light absorption C) to be able to observe at radio wavelengths D) to reduce light pollution E) to be able to observe at infrared wavelengths

C) to be able to observe at radio wavelengths

Which of the following is a principal advantage of CCDs over photographic film? A) CCDs can be attached to modern telescopes more easily than cameras. B) CCDs allow long exposures (e.g., minutes or hours), and film does not. C) Images recorded with CCDs never require any image processing, while images recorded by film often do. D) CCDs capture a much higher percentage of the incoming photons than does film. E) CCDs can record the colors of astronomical objects accurately, while film cannot.

D) CCDs capture a much higher percentage of the incoming photons than does film.

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? A) It can observe infrared and ultraviolet light, as well as visible light. B) Stars do not twinkle when observed from space. C) It never has to close because of bad weather. D) It is closer to the stars. E) Observers on the ground can use it at any time of day (i.e., not only during their night).

D) It is closer to the stars.

Why do astronomers need different telescope designs to observe across the electromagnetic spectrum? A) Light pollution is worse at radio wavelengths than visible wavelengths. B) Telescopes have to adapt to the greater distortion of the atmosphere at shorter wavelengths. C) Astronomers and engineers enjoy the challenge of making new telescope designs. D) Photons of different energy behave differently and require different collection strategies. E) New telescopes incorporate new technology to increase their efficiency.

D) Photons of different energy behave differently and require different collection strategies.

Which of the following wavelength regions cannot be studied with telescopes on the ground? A) radio waves B) X rays C) ultraviolet D) both B and C E) both A and C

D) both B and C

If you had only one telescope and wanted to take both visible-light and ultraviolet pictures of stars, where should you locate your telescope? A) on Earth's surface B) on a tall mountain C) in an airplane D) in space

D) in space

What is the purpose of adaptive optics? A) to increase the magnification of telescopes on the ground B) to increase the collecting area of telescopes on the ground C) to improve the angular resolution of telescopes in space D) to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground E) to allow several small telescopes to work together like a single larger telescope

D) to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground

Suppose the angular separation of two stars is smaller than the angular resolution of your eyes. How will the stars appear to your eyes? A) You will not be able to see these two stars at all. B) The two stars will appear to be touching, looking rather like a small dumbbell. C) You will see two distinct stars. D) You will see only the larger of the two stars, not the smaller one. E) The two stars will look like a single point of light.

E) The two stars will look like a single point of light.

Improvements in technology will eventually allow the entire electromagnetic spectrum to be observed from high mountaintop observatories. True False

False

Professional astronomical telescopes generally have a much greater magnification than the telescopes you can buy in stores. True False

False

______________________ separate the various colors of light, allowing astronomers to determine stellar composition and many other stellar properties.

Spectrographs

Most astronomical objects emit light over a broad range of wavelengths. True False

True

The lens in your eye forms an upside-down image of the world. True False

True

X rays from astronomical objects can only be detected from telescopes in space. True False

True

A 10-meter telescope has a larger ______________________ than a 4-meter telescope.

light-collecting area

The large research observatories on Mauna Kea use giant _______________.

reflecting telescopes

Galileo's telescope designs using lenses were examples of ____________________.

refracting telescopes

Which of the following forms of light can be observed with telescopes at sea level? Select all that apply. X rays ultraviolet light visible light infrared light radio waves

visible light and radio waves