Chapter 3 Flashcards
If you throw a rock into a pond, it creates a wave in the water. What is responsible for creating an electromagnetic wave?
A vibrating charged particle
The number of waves that pass a point each second measures ________.
frequency
For a wave of constant velocity, such as an electromagnetic wave, how are the wavelength and frequency related?
Wavelength is inversely proportional to the frequency.
Which of the following types of electromagnetic waves has the shortest wavelength?
X-ray
Electromagnetic (EM) radiation penetrates the atmosphere of Earth at what portions of the electromagnetic spectrum?
In visible, some IR, and some radio wavelengths
What fraction of the entire electromagnetic spectrum is spanned by visible light?
Visible light covers a tiny fraction of the electromagnetic spectrum.
The energy of a photon is inversely proportional to the wavelength of the radiation.
True
What would you need to obtain a successful X-ray image of a high-energy source?
- A telescope designed and built to be launched into space.
2. A cosmic source of high temperature.
The term seeing is used to describe how faint an object can be detected by a telescope.
False
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.
True
Gamma-ray telescopes employ the same basic design that optical instruments use.
False
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
If we double the diameter of a telescope’s mirror, what happens to its light-gathering ability?
Light-gathering ability quadruples. (1/4)
What property of a telescope influences its resolving power?
The size of the main mirror or lens
What is meant in astronomy by the phrase “active 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 is an advantage the Hubble Space Telescope has over ground-based telescopes?
There is no blurring due to the atmosphere.
What is the primary advantage of techniques of radio interferometry?
An increase in resolving power
Radio telescopes would NOT represent a good choice for astronomical study of ________.
ordinary stars. Most ordinary stars produce little radio radiation and so are difficult to detect with radio telescopes.
What is the main reason that ultraviolet astronomy must be done in space?
Earth’s atmosphere absorbs most ultraviolet wavelengths.
Which of the following is true about the Spitzer Space Telescope?
It orbits the Sun a little behind Earth.
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.
Which of the following statements about the use of infrared telescopes is true?
The detector and telescope must be cooled to very low temperatures.
When multiple radio telescopes are used for interferometry, resolving power is most improved by increasing
the distance between telescopes.
The best way to study young stars hidden behind interstellar dust clouds would be to use
nfrared light.
