Astronomy Chapter 6

Rank the following types of electromagnetic radiation in order of decreasing wavelength: infrared, gamma-ray, radio, ultraviolet, visible.

radio, infrared, visible, ultraviolet, gamma-ray

Compared to infrared radiation, does gamma-ray radiation have longer or shorter wavelengths? longer shorter Does gamma-ray radiation have higher or lower energy per photon? higher lower

shorter higher

Does blue light have a higher or lower energy than red light? higher lower Does blue light have higher or lower frequency than red light? higher lower Does blue light have a longer or shorter wavelength than red light? longer shorter

higher higher shorter

Why are there arrays of many more than two radio telescopes working together? Every additional telescope added to the array increases the size of the effective telescope. Since it is the distance between the telescopes that is important, there is no need for an array of more than two telescopes. Additional telescopes in between the two farthest-separated telescopes increases the gathering power and resolving power of the effective telescope. Additional telescopes in different locations (especially remote locations) give a greater chance of one of them not being subject to interference.

Additional telescopes in between the two farthest-separated telescopes increases the gathering power and resolving power of the effective telescope.

We say light is a wave. For light, what's waving? Space itself. Space and time. Electric and magnetic fields. Electric and magnetic forces.

Electric and magnetic fields.

Based on what you know about light, select all of the correct statements from the following list. High frequency photons carry more energy than long wavelength photons. Different types of electromagnetic radiation are fundamentally different types of waves. Light can act both as a wave and a particle. All electromagnetic waves travel at the speed of light. The only type of electromagnetic radiation that is actually considered light is visible light. X-rays and gamma rays are long wavelength photons. A photon is a particle of light.

High frequency photons carry more energy than long wavelength photons Light can act both as a wave and a particle. All electromagnetic waves travel at the speed of light. The only type of electromagnetic radiation that is actually considered light is visible light. A photon is a particle of light.

Why must telescopes observing at long infrared (that is, far-infrared) wavelengths be cooled to low temperatures? They must be cooled because objects emitting infrared radiation are hot, and observing them will heat up the telescope. This is done to match the relatively cool temperature of something emitting infrared radiation. If not cooled, the telescope will give off more infrared radiation than what it is observing. Actually, infrared telescopes do not have to be cooled any more than other telescopes.

If not cooled, the telescope will give off more infrared radiation than what it is observing.

Based on what you know about instruments used by astronomers to analyze light, select all of the correct statements from the following list. In most modern spectrographs, gratings have replaced prisms. Absolutely nothing is known about an object until its full spectrum is observed. Prisms and gratings spread light out into its spectrum by bending different wavelengths of light in different directions. Spectral lines observed from astronomical objects tell astronomers what atoms are present. The colors seen in all astronomical images are the true colors of the objects. Photography in astronomy has mostly been replaced by CCD imaging. Photometers are still necessary to measure the brightness of the images gathered by telescopes.

In most modern spectrographs, gratings have replaced prisms. Prisms and gratings spread light out into its spectrum by bending different wavelengths of light in different directions. Spectral lines observed from astronomical objects tell astronomers what atoms are present. Photography in astronomy has mostly been replaced by CCD imaging.

If two radio telescopes work together, which of the following is the size of the effective telescope? It is equal to the diameter of the smaller telescope, but with better resolution. It is equal to the diameter of the bigger telescope, but with better resolution. It is equal to the distance between the telescopes. It is equal to the diameter of the two telescopes put together.

It is equal to the distance between the telescopes.

What is the advantage of gathering more light in observations? Check all that apply. One can see dimmer objects. Diminishes the effect of seeing. Greater signal-to-noise ratio. Less chromatic aberration. Greater magnification.

One can see dimmer objects. Greater signal-to-noise ratio.

The primary mirror of telescope A has a diameter of 20 cm, and telescope B has a diameter of 100 cm. How do the light gathering powers of these two telescopes compare? Telescope A has 25 times the light gathering power of telescope B. Telescope B has 25 times the light gathering power of telescope A. The light gathering power depends on the focal length of the eyepiece also. Telescope B has 5 times the light gathering power of telescope A. Telescope A has 5 times the light gathering power of telescope B.

Telescope B has 25 times the light gathering power of telescope A.

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

Telescopes can collect far more light with far better angular resolution.

Based on what you know about telescopes located in space, select all of the correct statements from the following list. The Hubble Space Telescope makes observations at all wavelengths. Earth's atmosphere has no effect on visible light, so there is no need to place an optical telescope in space. Enough far-infrared energy gets to Earth's surface that far-infrared telescopes do not need to be put in orbit. Most types of electromagnetic waves are not visible to ground-based telescopes. There would be no limit to what an optical telescope in space could see. The Chandra, Spitzer, and Fermi Gamma-Ray telescopes are all in space.

The Chandra, Spitzer, and Fermi Gamma-Ray telescopes are all in space. Most types of electromagnetic waves are not visible to ground-based telescopes.

Why are near-infrared telescopes located on mountaintops and ultraviolet telescopes in Earth orbit? Ultraviolet telescopes require the low temperature of space to operate. The primary infrared blocker, water vapor, is mostly in the lower atmosphere and the primary ultraviolet blocker, ozone, is located high in the atmosphere, far above mountaintops. The primary infrared blocker, water vapor, is mostly in the lower atmosphere. The primary infrared blocker, water vapor, is mostly in the lower atmosphere and ultraviolet telescopes require the low temperature of space to operate. The primary ultraviolet blocker, ozone, is located high in the atmosphere, far above mountaintops.

The primary infrared blocker, water vapor, is mostly in the lower atmosphere and the primary ultraviolet blocker, ozone, is located high in the atmosphere, far above mountaintops.

Why do the pupils of a cat's eyes open wider at night? Because cats sleep all day and are wide awake at night. Cats are the only animals besides humans to observe the stars. To reduce the buildup of cat eye wax. To increase light gathering power. To attract a mate.

To increase light gathering power.

Why must far-infrared telescopes be cooled to a low temperature? To improve their poor magnifying power. To make use of the vast supplies of helium stockpiled by the United States. To protect the sensitive electronic amplifiers from overheating by sunlight. To reduce interfering heat radiation emitted by the telescope. To improve their poor resolving power.

To reduce interfering heat radiation emitted by the telescope.

What is a disadvantage of radio telescopes compared to optical telescopes? Radio telescopes require much more land, due to the long wavelengths of radio waves. This can provide challenges for supporting radio dishes. Radio waves from cosmic sources have much lower intensities than those from Earth-based sources, such as radio stations. Radio telescopes have poor resolving power, due to the long wavelengths of radio waves. all of the above

all of the above

What do the newer light-sensitive electronic CCD chips do better than the older photographic plates coated with light-sensitive chemicals? all of the below They have a greater sensitivity to light. They can detect both bright and dim objects in a single exposure. Photometry can be done with the CCD images The CCD images are easier to manipulate.

all of the below

Why have no large refracting telescopes been built since 1900? all of the below Refracting telescopes suffer from chromatic aberration. Making large glass lenses without interior defects is difficult. Refracting telescopes have several surfaces to shape and polish. Large glass lenses are more difficult to support than large mirrors. Correct: Your answer is correct.

all of the below

Why are telescopes in different locations working together especially desirable for radio telescopes? because of the high intensity of radio sources because they can avoid interference from a single location because radio telescopes have such poor resolution because radio telescopes are so large

because radio telescopes have such poor resolution

In general, does a telescope resolve a close double star, such as in the figure below, better at blue wavelengths or red? blue wavelengths red wavelengths How do you know? Observations at shorter wavelengths resolve larger angular sizes than observations at longer wavelengths. Observations at shorter wavelengths resolve smaller angular sizes than observations at longer wavelengths. Blue light bends more than red light when it refracts through a telescope lens. Blue light bends less than red light when it refracts through a telescope lens.

blue wavelengths Observations at shorter wavelengths resolve smaller angular sizes than observations at longer wavelengths.

Rank the following colors of visible light in order of increasing wavelength: blue, green, red, yellow.

blue, green, yellow, red

If the frequency of an electromagnetic wave increases, does the number of wave peaks passing by you increase, decrease, or stay the same? increase decrease stay the same Does the wavelength increase, decrease, or stay the same? increase decrease stay the same Does the energy of the photon increase, decrease, or stay the same? increase decrease stay the same

increase decrease increase

When telescopes in different locations work together, it is called which of the following? interferometry amplification spectroscopy adaptive optics

interferometry

Which theoretical power of an optical telescope is determined by the diameter of the primary mirror or lens? magnifying power resolving power light gathering power and resolving power light gathering power light gathering power and magnifying power

light gathering power and resolving power

Which power of a telescope is the least important? light gathering power resolving power light gathering power and resolving power light gathering power and magnifying power magnifying power

magnifying power

Rank the following colors of visible light in order of increasing frequency: green, red, violet, yellow.

red, yellow, green, violet

Which power of a large ground-based optical telescope is severely limited by Earth's atmosphere on a cloudless night? magnifying power resolving power light gathering and resolving power light gathering and magnification light gathering power

resolving power

Which power of a telescope might be expressed as "0.5 seconds of arc"? light gathering power magnifying power light gathering power and magnifying power light gathering power and resolving power resolving power

resolving power

Does a 840 nm photon travel faster than, slower than, or the same speed as a 430 nm photon? faster slower same speed

same speed

Different wavelengths of light are refracted different amounts. Which wavelengths are bent by the greatest amount? short wavelengths long wavelengths wavelengths intermediate between long and short wavelengths can not be determined from the figure none of the above

short wavelengths

The visible part of the electromagnetic spectrum can be divided into seven color bands: red, orange, yellow, green, blue, indigo, and violet (from long to short wavelength). A single photon of which of these colors has the greatest amount of energy? violet orange red green blue

violet

The entire electromagnetic spectrum can be divided into seven bands: radio, microwave, infrared, visible, ultraviolet, X ray, and gamma ray (from longest to shortest wavelength). To which of these two bands is Earth's atmosphere the most transparent? visible and radio X ray and gamma ray ultraviolet and infrared microwave and radio visible and ultraviolet

visible and radio