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27 Cards in this Set

  • Front
  • Back
What is light?
Light, more properly "visible light", is one form of electromagnetic radiation. All electromagnetic radiation (radio waves, infrared radiation, visible light, ultraviolet radiation, X rays, and gamma rays) has both wave and particle properties.
What type of electromagnetic radiation is most dangerous to life?
Gamma rays are most dangerous

UV light from sun is the most common though.
What is the main purpose of a telescope?
A telescope is designed primarily to collect as much light as possible.
Why do stars twinkle?
Rapid changes in density of the Earth's atmosphere cause passing starlight to change direction, making stars appear to twinkle.
What type(s) of electromagnetic radiation can telescopes currently detect?
Telescopes have been built tat can observe the entire electromagnetic spectrum.
______, compact units of vibrating electric and magnetic fields, all carry energy through space at the same speed, "the speed of light" (300,000 km/s in a vaccuum, slower in any medium).
Radio waves, infrared radiation, visible light, ultraviolet radiation, X rays, and gamma rays are the forms of ____________ __________. They travel as photons, sometimes behaving as particles, sometimes as waves.
electromagnetic radiation
________ light occupies only a small portion of the electromagnetic spectrum.
The wavelength of a visible light photon is associated with its _______. Wavelengths of visible light range from about 400 nm for _______ light to 700 nm for _______ light.
Infrared radiation and radio waves have wavelengths ______ than those of visible light. UV light, X rays, and gamma rays have wavelengths that are _______.
The motion of an object toward or away from an observer causes the observer to see all the colors from the object to __________ or _________, respectively. This is generically called _________ shift.
A telescope's most important function is to gather as much _______ as possible. Its second function is to reveal the observed object in as much detail as possible. Often the least important function of a telescope is to ________ objects.
_________ telescopes, or __________, produce images by reflecting light rays from concave mirrors to a focal point or focal plane.
_________ telescopes, or __________, produce images by benging light rays as they pass through glass lenses. Glass impurity, opacity to certain wavelengths, and structural difficulties make inadvisable to build extremely large refractors. __________ are not subject to many of the problems that limit the usefullness of refractors.
What are used to record images?
Charged-coupled devices (CCD's)
__________ telescopes are being built with active and adaptive optics. These advanced technologies yield resolving power comparable to the Hubble Space Telescope.
________ telescopes have large reflecting antennas (dishes) that are used to focus radio waves.
Very sharp radio images are produces with arrays of radio telescopes linked together in a technique called ____________.
The Earth's atmosphere is fairly transparent to most visible light and radio waves, along with some infrared and UV radiation, arriving from space, but it absorbs much of the _______________ __________ at other wavelengths.
electromagnetic radiation
Explain some of the advantages of relecting telescopes over refracting telescopes.
1. glass impurity
2. opacity to certain wavelengths
3. structural difficulties
4. can't build big ones

1. don't have those problems
What are the three major function of the telescope?
1. (most important) to gather as much light as possible.
2. reveal the observed object in as much detail as possible.
3. (least important) to magnify objects
T or F

An light wave always has to travel through a medium.
Do we consider, for astronomy, a photon to be a wave or particle?
What is angular resolution?
It measures the clarity of the image
Why must astronomers use satellites and Earth-orbiting observatories to study the heavens at X-ray wavelengths?
Because they don't penetrate through the Earth's atmosphere because of the different gases in atmosphere.
What are NASA's 4 great observatories and in what parts of the electromagnetic spectrum do they observe?
Hubble Space Telescope -observes the Universe at ultraviolet, visual, and near-infrared wavelengths

Compton Gamma Ray Observatory - gamma ray

Chandra X-ray Observatory - X-ray

Spitzer Space Telescope - thermal infrared rays
Why did Romer's observations of the eclipses of Jupiter's moons support of the heliocentric, but not the geocentric, cosmology?
because when Jupiter and the Earth are in opposition, when they are on the same side as the sun, The Earth-Jupiter distance is relatively short compared to when Jupiter is near conjunction.