6.2.3 EM Waves & Matter

• What are electromagnetic (EM) waves?

  Transverse waves that transfer energy through space or matter without requiring a medium.
• What is the order of the electromagnetic spectrum from longest wavelength to shortest wavelength?

  • Radio waves
  • Microwaves
  • Infrared (IR)
  • Visible light (ROYGBIV: Red, Orange, Yellow, Green, Blue, Indigo, Violet)
  • Ultraviolet (UV)
  • X-rays
  • Gamma rays
• How do the properties of EM waves change as you move from radio waves to gamma rays?

  The wavelength decreases, while frequency and energy increase.
• What are radio waves primarily used for?

  Communication, such as TV and radio broadcasting.
• What is the primary use of microwaves?

  Cooking food in microwave ovens and satellite communication.
• What are infrared waves used for?

  Remote controls, thermal imaging, and night-vision equipment.
• What is the significance of visible light in the electromagnetic spectrum?

  It is the only part of the spectrum visible to the human eye and is essential for seeing.
• What are the effects of ultraviolet (UV) rays?

  They can cause skin tanning and are used in fluorescent lamps, but can be harmful in excess.
• What is the primary use of X-rays?

  Medical imaging to view inside the body.
• What are gamma rays used for?

  Cancer treatment and sterilizing medical equipment.
• What are the different interactions of EM waves with matter?

  • Reflection: EM waves bounce off a surface.
  • Refraction: EM waves change direction when passing from one medium to another.
  • Diffraction: EM waves spread out after passing through a gap or around an obstacle.
  • Absorption: Matter absorbs EM waves, converting them into heat.
  • Transmission: EM waves pass through a medium without being absorbed.
• What is the speed of EM waves in a vacuum?

  Approximately \( 3 \times 10^8 \) meters per second.
• What is the wave equation that relates wave speed, wavelength, and frequency?


  The equation is \( c = \lambda \times f \).
• What happens to frequency when the wavelength increases, given that the speed of light is constant?

  The frequency decreases.
• What are the dangers associated with UV rays?

  They can cause skin cancer.
• What are the dangers associated with X-rays and gamma rays?

  They can damage cells and lead to cancer if exposure is high.
• What are some practical applications of EM waves?

  • Infrared cameras for detecting heat.
  • X-ray machines in hospitals.
  • Satellite communication using microwaves.
  • UV sterilization for killing bacteria.
• What key points should be remembered about EM waves?

  • The energy of EM waves increases with frequency.
  • Higher frequency EM waves have more energy and can be more dangerous.
  • EM waves can be reflected, refracted, diffracted, and absorbed.