Quick Recap — The Electromagnetic Spectrum

  • Increasing frequency (decreasing wavelength): radio →\to microwave →\to infrared →\to visible →\to ultraviolet →\to X-ray →\to gamma.
  • Visible light: roughly 400 nm (violet) to 700 nm (red).
  • Uses: radio (communication), microwave (radar, ovens), infrared (heat and remote controls), UV (sterilization), X-rays (imaging), gamma rays (nuclear and medical).
  • All EM waves travel at cc in vacuum; the photon energy is proportional to frequency (gamma rays are the most energetic).
  • Gamma rays have the shortest wavelength and greatest penetrating power; radio waves have the longest wavelength.