Astronomy 123 Basics   Light and Electromagnetic Radiation

• We learn about the stars by studying the electromagnetic radiation that they emit.

• Light is one particular type of electromagnetic radiation.

• The other types of electromagnetic radiation are:
• radio
• infrared
• ultraviolet
• X rays
• Gamma rays

• Electromagnetic radiation is a wave with a wavelength and an amplitude.

• The frequency of a wave is related to its velocity and wavelength through the formula
• wavelength x frequency = velocity

• Since electromagnetic radiation (or waves) travel at the speed of light (300,000 kilometers/second) we have a relationship between wavelength and frequency.

• The electromagnetic spectrum ranges from radio waves at one extreme to gamma rays at the other extreme.

• Radiation is composed of "photons" (packets of electromagnetic radiation)
  • the "photons" have energies related to the "color" or wavelength
    • short wavelengths -> higher energies
      • like gamma rays
    • long wavelengths -> lower energies
      • like radio waves

• Visible light can be split into its components by a prism.
  • the bending of light in going through the prism results from REFRACTION
  • short wavelengths (red) are refracted less, than long wavelengths (blue and violet)

• The entire electromagnetic spectrum shows the frequencies and wavelengths of the types of electromagnetic radiation.

• The atmosphere blocks much of the electromagnetic radiation from space.  There are "windows" of transparency in the radio and visible parts of the spectrum.

Electromagnetic Radiation - Encyclopedia Britannica