54 terms


current understanding of nature of light emerged
showed that light sometimes behaves as particles and sometimes as waves
wave model
wavelengths of radiation vary
white light
consists of several wavelengths corresponding to the colors of the rainbow
particle model
exert a pressure called radiation pressure on matter
particle model
shorter wavelengths correspond to more energetic photons
light comes from
movement of electrons in atoms
contains protons and neutrons
atoms with the same number of protons
atoms with varying numbers of neutrons
atoms with varying numbers of electrons
spectral lines
when electron jumps form one energy level to another
186,000 m/s
speed of light
visible light
only one small part of an array of energy
electromagnetic radiation
gamma rays, x-rays, UV light, visible light, infrared light, radio waves
visible light
only one type of electromagnetic radiation emitted by stars
each type of EM radiation
travels at exactly the same speed (speed of light)
peak color (wavelength)
shifts to shorter wavelengths as an object is heated
inversely proportional to temperature
emits all colors
most intensely emits blue-green part of spectrum
learned by analyzing starlight
chemical composition
learn by analyzing starlight
study of properties of light that depend on wavelength
light pattern produced by passing light through a prism which spreads out the various wavelengths
continuous spectrum
produced by an incandescent solid, liquid, or high pressure gas
continuous spectrum
uninterrupted band of color
dark-line (absorption) spectrum
produced when light is passed through a comparatively cool, low pressure gas
dark-line (absorption) spectrum
appears as a continuous spectrum but with dark lines running through it
bright-light (emission) spectrum
produced by a hot (incandescent) gas under low pressure
bright-light (emission) spectrum
appears as a series of bright lines of particular wavelengths depending on the gas that produced them
dark-line (absorption) spectrum
most stars have
instrument used to spread out the light
emission and absorption spectra
allow astronomers to determine the elements present in a distant star
each chemical element
produces its own unique set of spectral lines when it burns
brightness of spectral lines
depend on conditions in spectrum's source
continuous spectrum
produced by a hot,dense gas or object - is a complete rainbow of colors without any specific spectral lines
emission line spectrum
produced by hot, rarefied gas - series of bright spectral lines against a dark background
absorption line spectrum
produced by a cool gas in front of a continuous light - series of dark spectral lines among the colors of the rainbow
learned by analyzing starlight
doppler shift
allows astronomers to measure radial velocity
spectral lines
shift due to relative motion between the source and the observer
doppler effect
apparent change in wavelength of radiation caused by the relative motions of the source and observer
doppler effect
used to determine increasing distance (wavelength stretches)
doppler effect
used to determine decreasing distance (wavelength compresses)
larger doppler shifts indicate higher velocities
red shift
distance between the observer and the sources is increasing
blue shift
distance between the observer and the source is decreasing
radial velocity
learned by analyzing starlight
different types of EM radiation
require different types of telescopes
refracting telescope
uses a lens to concentrate incoming light
reflecting telescope
uses mirrors to concentrate incoming starlight
not all EM radiation
can penetrate earth's atmosphere