The Universe

• What does the study of atomic absorption spectra allow us to determine?

  The chemical make-up of stars
• What does the study of atomic absorption spectra show about galaxies?

  They are moving away from us
• What is a continuous emission spectrum?

  • A complete spectrum of colors
  • Shows all wavelengths of light
  • Produced by light sources like stars or filament bulbs
• How does a hot gas emit light?

  It emits certain wavelengths of light
• What is a line emission spectrum?

  A series of bright lines on a dark background
• What does a gas cloud produce when it is on its own?

  A line emission spectrum
• What happens when a continuous spectrum travels through a cooler gas?

  It absorbs certain wavelengths of light
• What is a line absorption spectrum?

  • A series of dark lines on a continuous spectrum
  • Produced by a cool gas with a hot source behind it
  • Indicates wavelengths absorbed by the gas
• What do black hydrogen absorption lines correspond to?

  Bright hydrogen emission lines
• How are line emission spectra unique to elements?

  • Each element produces a different line spectrum
  • Line spectra can identify the element present
  • Similar to a fingerprint for elements
• How can you identify an unknown element using atomic spectra?

  By comparing its line spectra
• What is the significance of Fraunhofer lines in spectroscopy?

  • They indicate absorption lines in a spectrum
  • Help identify elements in stars
  • Show the presence of cooler gases
• Who invented the spectroscope?

  Joseph von Fraunhofer
• What do Fraunhofer lines represent?

  Dark lines on a continuous spectrum
• How are absorption lines produced?

  Gas atoms absorb certain wavelengths of light
• What can scientists determine from the line absorption spectrum of the Sun?

  What elements are present in its atmosphere
• Which elements can be identified in the Sun's atmosphere?

  Sodium, iron, calcium, magnesium
• What does the line emission spectrum of an element show?

  The specific wavelengths emitted by that element
• How do scientists identify elements in a gas cloud?

  By comparing absorption lines with emission spectra
• What happens when light from a distant gas cloud is examined?

  It shows a line absorption spectrum
• Which element is indicated to be in the gas cloud if the absorption lines match hydrogen's emission lines?

  Hydrogen
• What is the significance of the cosmological red shift?

  • Indicates galaxies are moving away
  • Supports the expanding Universe theory
• What is the role of the cosmic microwave background radiation?

  • Evidence of the Big Bang
  • Provides information about the early Universe
• These are Fraunhofer lines

  
• What does the study of atomic absorption spectra allow us to determine?

  The chemical make-up of stars
• What does the cosmological red shift indicate about galaxies?

  They are moving away from us in an expanding Universe
• What is the definition of wavelength?

  • The length of a single wave
  • Measured from one wave peak to the next
• How does the movement of an ambulance affect the sound wavelength heard by an observer?

  It compresses the wavelength when approaching
• What happens to the sound wavelength when an ambulance moves away from an observer?

  It stretches the wavelength
• What is the Doppler shift?

  The change in wavelength caused by movement
• What is red shift in terms of light wavelengths?

  Light wavelengths are stretched by movement away
• What is blue shift in terms of light wavelengths?

  Light wavelengths are compressed by movement towards
• Who is Edwin Hubble?

  An important observational cosmologist
• What did Hubble notice about the absorption spectrum lines from galaxies?

  They showed the same pattern as the Sun's spectrum
• What does the red shift of galaxies indicate about their movement?

  They are moving away from us
• What does the cosmological red shift provide evidence for?

  The expansion of the Universe
• What causes the cosmological red shift?

  • Light passing through expanding space
  • Stretching of wavelengths due to increasing distance
• What does the study of atomic absorption spectra allow us to determine?

  The chemical make-up of stars
• What does the cosmological red shift indicate about galaxies?

  Galaxies are moving away from us
• What does the expanding Universe imply about its structure?

  The Universe is continuously growing larger