AST CH 6

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

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

Suppose you want to determine the chemical composition of a distant planet or star. Which of the following will be most useful to have? high turbulence high angular resolution a radio telescope high spectral resolution

high spectral resolution

At which wavelength range is there no current or planned space observatory? visible radio X-ray infrared gamma-ray

radio

In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate? X-ray ultraviolet radio visible infrared

radio

Currently, the largest optical telescope mirrors have a diameter of 100 m. 5 m. 2 m. 10 m. 1 m.

10 m

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

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

Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light? Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light. Objects that emit radio waves are always much larger than objects that emit visible light, and therefore require larger telescopes. Radio telescopes are designed to collect sound rather than light. It is because radio telescopes are used in the daytime and visible light telescopes are used at night.

Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light.

The James Webb Space Telescope is scheduled to launch in 2018. In what range of the electromagnetic spectrum will it operate? X-ray Infrared Gamma-ray Radio

Infrared

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

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

What do we mean by the diffraction limit of a telescope? It describes the maximum exposure time for images captured with the telescope. It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images. It describes the farthest distance to which the telescope can see. It is the maximum size to which any telescope can be built.

It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images.

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

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

What is the purpose of adaptive optics? It reduces blurring caused by atmospheric turbulence for telescopes on the ground. It allows ground-based telescopes to observe ultraviolet light that normally does not penetrate the atmosphere. It is a special technology that allows the Hubble Space Telescope to adapt to study many different types of astronomical objects. It allows several small telescopes to work together like a single larger telescope.

It reduces blurring caused by atmospheric turbulence for telescopes on the ground.

What do astronomers mean by light pollution? Light pollution is a term used to describe the appearance of the sky in regions that are crowded with stars. Light pollution means contamination of light caused by chemicals in the Earth's atmosphere. Light pollution is a type of air pollution created by lightweight gases such as hydrogen and helium. Light pollution is light from human sources that makes it difficult to see the stars at night.

Light pollution is light from human sources that makes it difficult to see the stars at night.

Why do astronomers need different telescope designs to observe across the electromagnetic spectrum? Light pollution is worse at radio wavelengths than visible wavelengths. New telescopes incorporate new technology to increase their efficiency. Photons of different energy have different wavelengths, some of which are not accessible from Earth's surface and require different collection strategies. Telescopes have to adapt to the greater distortion of the atmosphere at shorter wavelengths. Astronomers and engineers enjoy the challenge of making new telescope designs.

Photons of different energy have different wavelengths, some of which are not accessible from Earth's surface and require different collection strategies.

In what wavelength range was interferometry first routinely used? radio infrared ultraviolet optical X-ray

Radio

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

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

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

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

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

bending of light rays by turbulent layers in the atmosphere

What does angular resolution measure? the number of electromagnetic waves captured by an image the size of an image the brightness of an image the angular size of the smallest features that the telescope can see

the angular size of the smallest features that the telescope can see

Which of the following effects is caused by atmospheric turbulence? twinkling of stars light pollution diffraction of light magnification of images

twinkling of stars