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
