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Astronomy Chapters 4,5
first test
57
Astronomy
Undergraduate 1
02/18/2011

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Term
Index of Refraction
Definition
n=c/v
Term
electric force
Definition
push or pull between electrically charged particles
Term
magnetic force
Definition
force between electrically charged particles arising from their motion
Term
electromagnetic wave
Definition
an accelerating charged particle
Term
amplitude
Definition
maximum deviation from its undsiturbed or relaxed position. The height it reaches from a straight line
Term
frequency
Definition
number of wave crests passing a point in space each second. Unit=cycles per second
Term
hertz
Definition
the unit of frequency/cycles per second
Term
period
Definition
time taken for one complete cycle
Term
wavelength
Definition
distance a wave travels during one complete oscillation
Term
spectrum
Definition
light spread out according to wavelength
Term
micrometer/micron
Definition
unit for measuring the wavelength of electromagnetic radiation. 10^-6
Term
electromagnetic spectrum
Definition
the whole range of different wavelengths of light
Term
ultraviolet (UV) radiation
Definition
light with wavelengths between 40 and 350 nm
Term
X-rays
Definition
wavelengths shorter than 40 nm
Term
gamma rays
Definition
shortest wavelength shorter than 10^-10 meter
Term
infrared radiation
Definition
light covering wavelengths between 700 nm and 500 micrometers
Term
microwave radiation
Definition
wavelengths longer than infrared, between radio
Term
radio waves
Definition
longest wavelength
Term
photoelectric effect
Definition
the emission of electrons from surfaces when the surfaces are illuminated by electromagnetic radiation greater than a certain frequency
Term
Planck's constant
Definition
6.63x10^-34 joule/second
Term
intensity
Definition
measures the total amount of energy a beam of light carries
Term
quantized
Definition
energy of light as broken into discrete packets called photons
Term
quantum of light
Definition
what a photon is referred to as
Term
quantum mechanics
Definition
branch of physics that deals with quantization of energy
Term
Heisenberg uncertainty principle
Definition
we cannot know both the precise momentum and position of a particle
Term
emission
Definition
the production of a photon when an atom decays to a lower-energy state
Term
emission line
Definition
bright, single colored feature in the spectrum of the cloud of gas
Term
The Doppler Effect
Definition
the motion of a source toward or away from us changes the wavelength of the waves reaching us
Term
redshift
Definition
star moving away
Term
blueshift
Definition
star moving towards us
Term
radial velocity
Definition
the rate at which the distance between you and the object is changing
Term
luminosity
Definition
power (energy per second, watts) radiated
Term
blackbody
Definition
emits as much thermal radiation as it absorbs
Term
blue means
Definition
hot
Term
red means
Definition
not
Term
twice as far
Definition
1/4 as bright
Term
albedo
Definition
the fraction of the sunlight that is reflected from a planet
Term
refracting telescope
Definition
use lenses instead of mirrors
Term
reflecting telescope
Definition
uses spherical mirrors
Term
objective lens
Definition
curved surface refract the light from a distant object
Term
focal plane
Definition
perpendicular to the optical axis of the telescope, images form
Term
aperture
Definition
the diameter of the objective lens
Term
focal length
Definition
distance between the telescope lens and the images formed
Term
compound lenses
Definition
minimize chromatic aberration. Used by refracting telescopes
Term
primary mirror
Definition
specially curved mirror that sends an image to the focal point in a reflecting mirror
Term
secondary mirror
Definition
folds light path from primary mirror to focal plane. Allows significant reduction in the length and weight of the telescope
Term
resolution
Definition
how clos two points of light can be to each other before a telescope is no longer able to split light into two seperate images
Term
diffraction limit
Definition
limiting resolution that a given telescope can achieve
Term
astronomical seeing
Definition
limit on the resolution of a telescope on the surface of Earth caused by this atmospheric distortion
Term
wavefront
Definition
light from a distant star arrivs at the top of Earth's atmosphere as a series of flat, parallel waves
Term
integration time
Definition
limited time interval in which the eye can add up photons
Term
quantum efficiency
Definition
likelihood that a particular photon landing on the retina will produce a response
Term
charge-coupled device CCD
Definition
imaging application detector for telescopes. astronomers detector of choice
Term
spectrographs-spectrometers
Definition
disperse light into its component wavelengths
Term
spectroscopy
Definition
study of an objects electromagnetic radiation
Term
radio telescope
Definition
uses radio waves to see sky
Term
interferometer (array)
Definition
two or more seperate telescopes that combine their signals to create a stronger signal (more than two telescopes in a pattern, attain and exceed angular resolution by other telescopes)
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