Example Chapter 5 Questions PDF

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Professor Tumakov...

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It is much easier to build large reflectors than large refractors. True

False

Chromatic aberration affects refractor and reflector telescopes equally, unless they have very long focal lengths. True

False CCD detectors gather light 10-20 times faster than the most sensitive photographic film. True

False

A convex lens is thinnest in its center; it refracts light to a focus, while a convex mirror reflects it to the focus instead. True False

Absorption of light passing through the glass is a bigger problem for Cassegrain reflectors than achromatic refractors. True

False

The light gathering ability of a telescope is most dependent on the diameter of it's primary objective.

True

False

Hubble Space Telescope is still the largest scope ever built. True

False

You could more easily resolve a close double star with a blue filter than with a red one. True

False One reason for building telescopes on mountain tops is that they improve seeing by reducing the amount of air above the observer. True

False

Optical telescopes are usually used only at night, but radio telescopes can be used day or night. True

False Radio telescopes have poorer angular resolution than optical telescopes because radio waves have a much longer wavelength than optical waves. True

False

All radio telescopes are reflectors in design True

False

Optical interferometry is more in use than radio interferometry. True

False

In addition to visible light, Hubble can do some work in the infrared and ultraviolet portions of the spectrum. True False

Due to our ozone layer, ultraviolet astronomy must be done from space. True

False

Galaxies look the same whether viewed in visible or X-ray wavelengths. True

False

The tendency of a wave to bend as it passes from one transparent medium to

another is called: reflection.

dispersion.

refraction.

diffraction.

interference.

What problem do refractor telescopes have that reflectors don't? light loss from secondary elements diffraction limited resolution

chromatic aberration

spherical aberration

bad seeing

This design involves only one optical surface, a concave mirror. prime focus reflector

Newtonian reflector Cassegrain reflector

Gregorian reflector

refractor

A major advantage of a Newtonian reflector over a refractor is its compact size.

the elimination of chromatic aberration.

there are only two lenses to grind.

the central hole in the mirror is smaller.

the elimination of the secondary mirror.

Why are most large telescopes reflectors, not refractors? Large lenses deform under their own weight, but mirrors can be supported.

Large mirrors need only one optical surface, achromats four surfaces to grind.

Reflectors do not suffer from chromatic aberration like refractors do.

Large, very clear lenses are harder to cast than more tolerant mirror blanks.

All of the above are correct.

The amount of diffraction and thus the resolution of the scope depends upon the wavelength used and the size of the main telescope objective lens or mirror.

the design of the eye piece

whether the telescope is a reflector or refractor. the brightness of the object.

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

The angular resolution of an 8 inch diameter telescope is ________ greater than that of a 2-inch diameter telescope. 2×

4×

8× 9×

16×

What is the resolution of a telescope? its ability to see very faint objects

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

its ability to make distant objects appear much closer to us its ability to separate light into its component colors for analysis

its ability to focus more than just visible light for imaging

What is the resolving power of the telescope? the ability to make distant objects appear closer

the ability to collect a lot of light

the ability to detect very faint objects

the ability to distinguish adjacent objects in the sky

the ability to separate light into its component colors

Compared to a 5 inch prime focus reflector, a 5-inch Newtonian reflector will have more light gathering power.

have the same light gathering power.

be easier to build.

will have more chromatic aberration.

Which method of astronomical measurement is the precise measurement of brightness? spectroscopy

photography astrometry

photometry

interferometry

Diffraction is the tendency of light to: spread around corners.

separate into its component colors.

bend through a lens.

disperse within a prism.

reflect off a mirror. It is diffraction that limits the ________ of a telescope of a given objective diameter. magnification

light grasp

resolution

aperture

interference

What are two advantages of large scopes over smaller ones? Large scopes have a larger field of view and sharper focus.

Large scopes are not subject to atmospheric turbulence and opacity like smaller ones.

Large scopes are easier to mount and control than small ones. Large telescope have more light grasp and better resolution.

Large telescopes give higher magnification and are easier to build.

The most important advantage of CCDs over film is that they record much more light in a given exposure time.

their images have more Megapixels

they record colors

they can cover larger areas of the sky than film can. their images automatically show the stars

Refractor telescopes suffer from this separation of light into its component colors. limited diffraction

spherical aberration

chromatic aberration

bad seeing refraction.

One advantage of the Hubble Space telescope over ground based ones is that it is larger than any Earth-based scopes.

it can better focus X-ray images.

it can make better observations of the ozone layer.

its adaptive optics controls atmospheric blurring better.

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

Green light has a shorter wavelength than orange light. In a 5 inch telescope, green light will provide better angular resolution than orange light.

come to the same exact focus as orange light.

provide worse angular resolution than orange light.

reduce the effects of atmospheric turbulence.

provide worse angular resolution than orange light

A mountain top is an especially good site for infrared telescopes since: there you are closer to celestial objects. you are above most of the carbon dioxide and water vapor in the atmosphere.

the cold weather helps the sensitivity of infrared detectors.

less air above means better seeing in many cases. All of the above are factors.

What problem does adaptive optics correct? defects in the optics of the telescope, such as the original Hubble mirror

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

the light pollution of urban areas

turbulence in the earth's atmosphere which creates twinkling chromatic aberration due to use of only a single lens objective

Which of the following is a problem inherent in all large radio telescopes? They are badly affected by poor seeing and atmospheric turbulence.

The lightest breeze shakes them, making the observations blurry.

Their waves are blocked by water vapor, so they must be located in deserts.

Radio waves have long wavelengths, so radio telescopes have poor resolution. The dust clouds in the Milky Way block almost all wavelengths except light.

Radio dishes are large in order to:

attract funding from NASA and the NSF

give greater magnification. increase their angular resolution and collect the very weak radio photons.

increase the range of waves they can collect.

detect shorter waves than optical telescopes for superior resolution.

Compared to optical telescopes, radio telescopes are built large because they're less expensive to make than optical telescopes.

radio photons don't carry much energy. and wavelength larger

atmospheric turbulence is more of a problem. radio sources are harder to find.

radio waves are absorbed by the atmosphere.

In astronomy, an interferometer can be used to yield better seeing conditions with optical telescopes

decrease the effects of light pollution in getting darker sky backgrounds

improve the angular resolution of radio telescopes increase the sensitivity of infrared telescopes to longer wavelengths

speed up the processing of CCD images...