Chapter 3

Question 1

If you throw a rock into a pond, it creates a wave in the water. What is responsible for creating an electromagnetic wave?

Answer 1

A vibrating charged particle

Question 2

The number of waves that pass a point each second measures ________.

Answer 2

frequency

Question 3

For a wave of constant velocity, such as an electromagnetic wave, how are the wavelength and frequency related?

Answer 3

Wavelength is inversely proportional to the frequency.

Question 4

Which of the following types of electromagnetic waves has the shortest wavelength?

Answer 4

X-ray

Question 5

Electromagnetic (EM) radiation penetrates the atmosphere of Earth at what portions of the electromagnetic spectrum?

Answer 5

In visible, some IR, and some radio wavelengths

Question 6

What fraction of the entire electromagnetic spectrum is spanned by visible light?

Answer 6

Visible light covers a tiny fraction of the electromagnetic spectrum.

Question 7

The energy of a photon is inversely proportional to the wavelength of the radiation.

Answer 7

True

Question 8

What would you need to obtain a successful X-ray image of a high-energy source?

Answer 8

1. A telescope designed and built to be launched into space.

2. A cosmic source of high temperature.

Question 9

The term seeing is used to describe how faint an object can be detected by a telescope.

Answer 9

False

Question 10

Radio telescopes are large in part to improve their angular resolution, which is poor because of the long wavelengths at which they are used to observe the skies.

Answer 10

True

Question 11

Gamma-ray telescopes employ the same basic design that optical instruments use.

Answer 11

False

Question 12

As telescopes become larger and larger, astronomers favor ________.

Answer 12

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

Question 13

If we double the diameter of a telescope’s mirror, what happens to its light-gathering ability?

Answer 13

Light-gathering ability quadruples. (1/4)

Question 14

What property of a telescope influences its resolving power?

Answer 14

The size of the main mirror or lens

Question 15

What is meant in astronomy by the phrase “active optics”?

Answer 15

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.

Question 16

Which of the following is an advantage the Hubble Space Telescope has over ground-based telescopes?

Answer 16

There is no blurring due to the atmosphere.

Question 17

What is the primary advantage of techniques of radio interferometry?

Answer 17

An increase in resolving power

Question 18

Radio telescopes would NOT represent a good choice for astronomical study of ________.

Answer 18

ordinary stars. Most ordinary stars produce little radio radiation and so are difficult to detect with radio telescopes.

Question 19

What is the main reason that ultraviolet astronomy must be done in space?

Answer 19

Earth’s atmosphere absorbs most ultraviolet wavelengths.

Question 20

Which of the following is true about the Spitzer Space Telescope?

Answer 20

It orbits the Sun a little behind Earth.

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

When multiple radio telescopes are used for interferometry, resolving power is most improved by increasing

Answer 23

the distance between telescopes.

Question 24

The best way to study young stars hidden behind interstellar dust clouds would be to use

Answer 24

nfrared light.