2 LESSON_Q2

• Regions of the electromagnetic spectrum

  • Radio waves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays
• Electromagnetic spectrum


  A continuum of electromagnetic waves arranged according to frequency and wavelength
• As you look from left to right on a diagram of the spectrum

  The wavelengths get smaller and the frequency gets larger
• There is an inverse relationship between the size of the wave and frequency
• All EM waves are radiation
• The longer wavelengths do not carry enough energy to damage cells
• The higher the frequency, the more energy in the wave
• Photons


  Bundles of wave energy
• Gamma rays have photons of high energies while radio waves have photons with the lowest energies
• Radio waves


  EM waves with wavelengths between 1 millimeter and 100 kilometers (or 300 GHz and 3 kHz in frequency)
• Radio waves are produced by making electrons vibrate in an antenna
• Radio waves are used to transmit sound and picture information over long distances
• The whole region of radio waves is divided into smaller regions
• EM Waves


  • Radio
  • Microwave
  • Infrared
  • Visible
  • UV
  • X-ray
  • Gamma ray
• Wavelength


  Distance between two consecutive peaks or troughs of a wave
• Frequency


  Number of wave cycles that pass a given point per unit of time
• Energy


  Capacity to do work or cause change
• Radio wave properties


  • Wavelength: >1 x 10-1 m
  • Frequency: < 3 x 10^9 Hz
  • Energy: <2 x 10-24 J
• Microwave properties


  • Wavelength: 1 x 10-3 – 1 x 10-1 m
  • Frequency: 3 x 10^9 – 3 x 10^11 Hz
  • Energy: 2 x 10-24 – 2 x 10-22 J
• Infrared properties


  • Wavelength: 7 x 10-7 – 1 x 10-3 m
  • Frequency: 3 x 10^11 – 4 x 10^14 Hz
  • Energy: 2 x 10-22 – 3 x 10-19 J
• Visible light properties


  • Wavelength: 4 x 10-7 – 7 x 10-7 m
  • Frequency: 4 x 10^14 – 7.5 x 10^14 Hz
  • Energy: 3 x 10-19 – 5 x 10-19 J
• UV properties


  • Wavelength: 1 x 10-8 – 4 x 10-7 m
  • Frequency: 7.5 x 10^14 – 3 x 10^16 Hz
  • Energy: 5 x 10-19 – 2 x 10-17 J
• 1. ray properties


  • Wavelength: 1 x 10-11- 1 x 10-8 m
  • Frequency: 3 x 10^16 – 3 x 10^19 Hz
  • Energy: 2 x 10-17 – 2 x 10-14 J
• Gamma ray properties


  • Wavelength: <1 x 10-11 m
  • Frequency: >3 x 10^19 Hz
  • Energy: >2 x 10-14 J
• Radio waves


  • Longest wavelength in EM spectrum
  • Produced by making electrons vibrate in an antenna
  • Used to transmit sound and picture information over long distances
• Radio wave frequency bands

  • Extremely Low Frequency (ELF): <3 kHz, >100 km
  • Very Low Frequency (VLF): 3-30 Hz, 10-100 km
  • Low Frequency (LF): 30-300 kHz, 1-10 km
  • Medium Frequency (MF): 300 kHz – 3 MHz, 100 m – 1 km
  • High Frequency (HF): 3-30 MHz, 10 – 100 m
  • Very High Frequency (VHF): 30-300 MHz, 1 – 10 m
  • Ultra High Frequency (UHF): 300 MHz – 3 GHz, 10 cm – 1 m
  • Super High Frequency (SHF): 3 – 30 GHz, 1 – 10 cm
  • Extremely High Frequency (EHF): 30 – 300 GHz, 1mm – 1 cm
• Low frequency radio waves


  • Suitable for communication over great distances
  • Curvature of earth limits range to about 80 km
  • Repeaters used to extend range
• High frequency radio waves


  • Can be reflected by ionosphere to transmit over great distances
• Medium and high frequency radio waves

  • Used for broadcasting by local radio stations
• Microwaves


  Electromagnetic waves with wavelengths ranging from 1 meter to 1 millimeter, or frequencies between 300 MHz and 300 GHz
• Infrared radiation


  • Emitted by all objects
  • Amount and wavelength depend on temperature
  • Below 500C, object emits only infrared
  • Above 500C, object emits both infrared and some visible light
• Infrared image


  • Dog's nose appears cold (blue)
  • Dog's eyes and mouth appear warm (red)
• Visible light spectrum


  • Portion of EM spectrum visible to human eye
  • Wavelengths from 740 nm (red) to 380 nm (violet)
• Colors in visible spectrum

  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet
• Ultraviolet radiation


  Electromagnetic radiation with wavelengths shorter than visible light, from 10 nm to 400 nm
• Ultraviolet radiation subcategories


  • UV-A: 320–400 nm
  • UV-B: 290–320 nm
  • UV-C: 220–290 nm
• 1. rays


  Electromagnetic waves with wavelengths from 0.01 to 10 nanometers, frequencies from 3x10^16 Hz to 3x10^19 Hz
• 1. rays


  • Long wavelength X-rays can penetrate flesh but not bones, used for medical imaging
  • Short wavelength X-rays can penetrate metals, used for industrial inspection
  • All X-rays are dangerous, can damage living cells and cause cancer
• Gamma rays


  • Highest energy, shortest wavelength electromagnetic radiation
  • Emitted by stars and radioactive substances
  • Can only be blocked by lead and thick concrete
• Gamma rays


  • Ionizing radiation, biologically hazardous