astronomy chapt 3

What is true of radio telescopes?

They have poorer angular resolution than a optical telescope of the same size.

What is the primary advantage of techniques of radio interferometry?

an increase in resolving power

Which of the following is/are true when comparing radio telesopes to optical telescopes?

radio telescopes can observe objects in the daytime radio telescopes can observe objects even when it's cloudy

It is diffraction that limits the ________ of a telescope of a given objective diameter.

resolution

chromatic aberration

the lens in a refracting telescope focuses red and blue light differently (the blue focus lying closer to the lens) associated w refraction

The most important advantage of CCDs over film is that...

they record much more light in a given exposure time

exposure time

time spent gathering light from a source. (Doubling the exposure time doubles the total amount of radiation captured)

What problem does adaptive optics correct?

turbulence in the Earth's atmosphere that creates twinkling

Which of the following is true about observations at wavelengths other than optical or radio?

Most observations at wavelengths other than optical or radio need to be conducted by space-based telescopes.

adaptive optics

Rapid modifications are made to the tilt and location of the elements of a telescope to correct for the effects of atmospheric and instrumental distortion.

Which of the following statements about the use of infrared telescopes is true?

The detector and telescope must be cooled to very low temperatures.

resolution of a telescope

ability to distinguish two adjacent objects close together in the sky

If you want to make a very dim object appear much brighter in an image photographed through a telescope, which of the following factors are important?

diameter of telescope and length of exposure

interstellar medium

diffused clouds of gas and dust (associated w radio waves)

The design of modern X-ray telescopes depends on

grazing incidence optics

When used in a single instrument to greatly enhance its resolution, the four separate mirrors of the VLT act as a(n) _____.

interferometer

Which of the following is NOT a reason to use a reflecting telescope rather than a refractor?

lenses are harder to focus than mirrors

The Arecibo radio telescope is laid out like which optical telescope design?

prime focus reflector

As telescopes become larger and larger, astronomers favor...

reflecting telescopes, in part because large lenses and mirrors sag under their own weight, and it is easier to support a mirror along its entire back side than it is to support a lens only around its edge

what was the earliest telescope?

refracting

Which of the following forms of light can be observed with telescopes at sea level?

visible, radio