SC10-2

    Cards (24)

    • Electromagnetic waves
      • Disturbances that transfer through field
      • Transverse waves
      • Can travel through a medium or in vacuum at the speed of light
      • Produced by accelerating electrons
      • Combination of electric and magnetic fields that oscillate perpendicular to each other and to the direction of the wave
    • Wave speed, frequency, and wavelength
      Related by the equation: v=λf, where v is wave speed, f is frequency, and λ is wavelength
    • Scientists who contributed to electromagnetic wave theory
      • Andre Marie Ampere
      • Michael Faraday
      • Heinrich Rudolf Hertz
      • James Clark Maxwell
      • Hans Christian Oersted
    • Electromagnetic spectrum
      Continuum of electromagnetic waves arranged according to frequency and wavelength
    • Regions of the electromagnetic spectrum
      • Radio waves
      • Microwaves
      • Infrared
      • Visible light
      • Ultraviolet
      • X-rays
      • Gamma rays
    • Radio waves
      • Longest wavelength in the EM spectrum
      • Produced by vibrating electrons in an antenna
      • Used to transmit sound and picture information over long distances
      • Divided into wavebands allocated to specific radio services
    • Low frequency radio waves

      • Suitable for communication over great distances, but limited by earth's curvature
      • Require repeaters to extend range
    • High frequency radio waves
      Can be reflected by the ionosphere to transmit over great distances
    • Microwaves
      • Smaller wavelength than radio waves
      • Used in satellite communications, radar, TV transmission, and cooking
    • Satellite communications using microwaves
      1. Microwaves transmitted by antenna to satellite
      2. Satellite amplifies and re-transmits signal to other antenna
    • Radar using microwaves
      1. Antenna whirls to scan area
      2. Transmitter sends out narrow beam of microwaves in pulses
      3. Distant object reflects signal back to receiver
      4. Direction and distance of object calculated
    • Terrestrial microwave communications
      Used for TV news coverage, cell phones, and microwave ovens
    • Infrared radiation
      • Lies beyond the red end of visible light
      • Emitted by all objects, amount and wavelength depend on temperature
      • Detected by infrared cameras and used in night vision, remote controls, and autofocus cameras
    • Visible spectrum
      Wavelengths of white light that the human eye can detect
    • Ultraviolet radiation

      • Shorter wavelength and higher energy than visible light
      • Used for sterilization, detecting forgeries, and producing vitamin D
      1. rays
      • Shorter wavelength and higher energy than UV
      • Penetrate flesh but not bones, used for medical imaging
      • Penetrate metals, used for industrial inspection
      • Dangerous due to ability to damage cells
    • Gamma rays

      • Shortest wavelength and highest energy in EM spectrum
      • Emitted by stars and radioactive substances
      • Can only be blocked by lead and thick concrete
      • Highly dangerous, used for cancer treatment and sterilization
    • Angle of incidence
      Angle between incident ray and normal
    • Angle of reflection
      Angle between reflected ray and normal
    • Laws of reflection
      1. Angle of incidence = angle of reflection
      2. Incident ray, normal, and reflected ray lie in the same plane
    • Specular reflection
      Parallel incident rays reflect as parallel rays
    • Diffuse reflection
      Incident rays are scattered in many directions
    • Reflection
      Light bounces off a surface
    • Refraction
      Light bends as it passes from one transparent substance into another