ASTR Chap 6
______________ refers to telescopic observations in which we separate an object's light so we can measure its intensity at different wavelengths.
Spectroscopy
What is meant by refraction of light
The Bending of light as it passes from one transparent medium to the next.
What does angular resolution measure?
The angular size of the smallest features that the telescope can see.
Suppose that two stars are separated in the sky by 0.01 arcsecond, and you observe them with a telescope that has an angular resolution of 1 arcsecond. What will you see?
The light from the two stars will be blended together so that they look like one star.
Which of the following determines the image quality of a telescope?
The light-collecting abilty and angular resolution
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 look like a single point of light.
t/f Improvements in technology will eventually allow the entire electromagnetic spectrum to be observed from high mountaintop observatories.
false
t/f A radio telescope and an optical telescope of the same size have the same angular resolution.
false
How much greater is the light-collecting area of a 6-meter telescope than a 3-meter telescope?
four times
A camera is an example of an instrument used for _____________ observations.
imaging
Where should you put a telescope designed for ultraviolet observations?
in Earth orbit
If you had only one telescope and wanted to take both visible-light and ultraviolet pictures of stars, where should you locate your telescope?
in space
Compare the light collecting ability of a telescope with an 8 inch diameter primary objective telescope to that of a telescope with a two inch primary objective.
it is 16 times greater
Human civilization is responsible for what astronomers call __________________________.
light pollution
What are the two most important properties of a telescope?
light-collecting area angular resolution
The twinkling of stars is caused by:
motion of air in our atmosphere
In what part of the electromagnetic spectrum do the biggest telescopes on Earth operate?
radio
Which of the following wavelength regions can be studied with telescopes on the ground?
radio, visible, and very limited portions of the infrared and ultraviolet regions
How much more light does an 8-meter telescope gather than a 2-meter telescope?
16 times as much
Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?
A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light.
What celestial coordinate tells you how far north or south the celestial object is located in the sky?
Declination
The James Webb Space Telescope is designed primarily to observe __________.
Infrared light
What does the technique of interferometry allow?
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?
It is a measure of how close two spectral lines can be distinguished.
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
It is closer to the stars.
What is meant by the resolution of an optical device?
It is the ability of an object fo form distinct images of two close objects
What do astronomers mean by light pollution?
Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.
What celestial coordinate tells you how far east or west a celestial object is in the sky?
Right Ascension
Which of the following is always true about images captured with X-ray telescopes?
They are always displayed in false color.
Which of the following is always true about images captured with X-ray telescopes?
They are always shown with colors that are not the true colors of the objects that were photographed.
What is the primary reason that we launch X-ray telescopes into space rather than building them on the ground?
X-rays from space do not reach the ground.
The familiar twinkling of the stars is caused by ___________, which also blurs telescopic images.
atmospheric turbulence
What causes stars to twinkle?
bending of light rays by turbulent layers in the atmosphere
If our eyes were sensitive only to X rays, the world would appear __________.
dark because X-ray light does not reach Earth's surface
Telescopes operating at this wavelength must be cooled to observe faint astronomical objects.
extreme infrared
Which of the following studies is best suited to a time monitoring experiment?
studying whether a particular star's brightness is steady or variable
If we want to confirm that a star's brightness alternately dims and brightens, we need ______________ observations of the star.
time monitoring
What is the purpose of adaptive optics?
to eliminate the distorting effects of atmospheric turbulence for telescopes on the ground
t/f X rays from astronomical objects can only be detected from telescopes in space.
true
Which of the following wavelength regions cannot be studied with telescopes on the ground?
ultraviolet X rays
Which of the following forms of light can be observed with telescopes at sea level?
visible light radio waves
