ASTR 1110 Chapter 6

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

10 m

What is the function of an eyepiece of a telescope? Bring the light to focus at a particular point. Spread the light out for better observing. Redirect the light back out to space. Separate the spectrum of light for a particular wavelength.

Bring the light to focus at a particular point.

You are using your friend's telescope to view a comet passing by the Earth. You recognize that you have to look from underneath the primary mirror. This telescope uses what focusing arrangement? prime focus Newtonian focus Cassegrain focus Galilean focus

Cassegrain focus

What is unique about observing radio waves on Earth? It can be done during the day. The telescopes are easily moveable. The detectors are faster than at other wavelengths. It is the only part of the electromagnetic spectrum that can enter the atmosphere.

It can be done during the day.

What do astronomers mean by light pollution? Light pollution refers to pollution caused by light industry as opposed to heavy industry. Light pollution refers to harmful gases emitted by common street lights. Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations. Light pollution is another name for sunlight which makes it impossible to see stars in the daytime.

Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.

Which of the following statements best describes the two principle advantages of telescopes over eyes? Telescopes can collect far more light with far better angular resolution. Telescopes can collect far more light with far greater magnification. Telescopes have much more magnification and better angular resolution. Telescopes collect more light and are unaffected by twinkling.

Telescopes can collect far more light with better 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? You will not be able to see these two stars at all. The two stars will look like a single point of light. The two stars will appear to be touching and look like a dumbbell. You will see two distinct stars.

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

The primary optical instrument in a refracting telescope is a mirror a lens an eyepiece a spectrum

a lens

The largest visible-light telescopes in the world today use what device as the primary collection of light? a lens a spectroscope a mirror a CCD

a mirror

Which of the following is not a detector of radiation that astronomers have used? a piece of photographic film a photographic plate a charge-coupled device a refracting telescope

a refracting telescope

To break up light into component colors that it contains astronomers use a device called: a telescope a CCD a spectrometer interferometer array

a spectrometer

The main purpose of using a telescope is to act as a bucket to collect light. get astronomers closer to the objects they are observing. shift all the electromagnetic radiation from space to the visible region. make the objects in space appear larger so that we can distinguish objects.

act as a bucket to collect light.

The size of the device that collects electromagnetic radiation is called a telescope's: magnification resolution aperture focal width

aperture

In a reflecting telescope the primary mirror is located at the bottom of the telescope tube. at the top of the telescope tube. suspended close to the top of the telescope tube. on the side of the telescope.

at the bottom of the telescope tube.

Why would an astro-photographer want to have a good motorized mount to set their telescope upon? because the Earth is rotating with the telescope attached to it. because astronomers typically have to look at many object in the sky in a few minutes. because all objects in the sky vary in brightness very quickly. because the telescope can then be moved out from under the clouds to where it is clear.

because the Earth is rotating with the telescope attached to it.

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

bending of light rays by turbulent layers in the atmosphere.

A new technique called adaptive optics allows astronomers to: change the eyepieces of their telescopes much more quickly than ever before. compensate for changes in the Earth's atmosphere and achieve better resolution. increase the aperture of their telescopes by connecting several telescopes. change the region of the electromagnetic spectrum in which their telescope is able to detect radiation.

compensate for changes in the Earth's atmosphere and achieve better resolution.

Detectors operating at this wavelength must be cooled to observe faint astronomical objects radio extreme infrared visible X-ray

extreme infrared

Order the following in order of increasing efficiency of detecting photons of visible light. eye; photographic film; CCD photographic film; CCD; eye CCD; eye; photographic film CCD; photographic film; eye

eye; photographic film, CCD

Which of these is not an issue in building a refracting telescope? making a very large piece of glass without bubbles or defects. chromatic aberration. finding an eyepiece that will work with the lens. building a large enough housing for the large lens with a long focal length.

finding an eyepiece that will work with the lens.

At the largest and most modern astronomical observatories on Earth today which of the following regularly happens to the image formed by the telescope? it is viewed by a group of graduate students who then make a sketch of it to have a permanent record. it is recorded on a piece of black and white film which is later developed. it is reflected by a special arrangement of mirrors back into the beam and up into the sky. it is recorded using an electronic detector like a CCD for later analysis.

it is recorded using an electronic detector like a CCD for later analysis.

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

radio

The largest telescopes in the world collect what region of light from the electromagnetic radiation? radio visible X-ray gamma

radio

The first telescopes and those used by Galileo were reflectors refractors radio telescopes Dobsonians

refractors

The ability of telescopes to provide precision of detail in an image is known as focusing resolution magnification aberration

resolution

The two regions of the electromagnetic spectrum where the Earth's atmosphere is transparent are visible light and: ultraviolet X-rays some radio waves gamma rays

some radio waves

A knowledgeable amateur astronomer tells you that she has a 14-inch telescope. What does the number 14 refer to? the number of times the image is magnified the length of the main telescope tube the focal length the diameter of the primary lens or mirror

the diameter of the primary lens or mirror

When astronomers design where to build a new and larger telescope which of the following is not an important part of how astronomers select a location? the place must have clear weather on as many nights as possible the place must be on a remote island or mountain the sky above the place must be dark (little light pollution) the place must be dry (low humidity)

the place must be on a remote island or mountain

Which of the following could not be determined by an observation that uses only spectroscopy? the chemical composition of a distant star the speed at which a distant galaxy is moving away from us the surface temperature of a distant star the size of a distant galaxy

the size of a distant galaxy

In order to collect more light astronomers must modify their telescopes. Which of these is not a way to improve observations? build larger optical devices put the telescope in orbit around the Earth use a smaller eyepiece build more sensitive detectors

use a smaller eyepiece

Which of the following types of telescopes can be used ONLY above the Earth's atmosphere? x-ray telescope visible-light telescope radio telescope reflector

x-ray telescope