Electromagnetic Waves

• The Earth is protected from harmful ultraviolet (UV) radiation from the sun by layer of ozone molecules found in the stratosphere
• Dobson unit (DU)


  A unit of measurement of atmospheric ozone, specifically in the stratosphere. One Dobson unit refers to a layer of ozone that would be 10 μm under standard temperature and pressure
• The Montreal Protocol signed by different countries in 1987 imposed restrictions on the use of CFCs and HBFCs
• Electromagnetic waves


  Produced by oscillating electric charges, with the electric field and the magnetic field vibrating perpendicularly to each other and to the direction of wave propagation
• It was only in 1887, through the efforts of Heinrich Hertz, a German physicist, that those waves (other than light) were observed to exist
• Electromagnetic wave equation

  v = f λ
• Electromagnetic spectrum


  The continuous range of electromagnetic waves arranged in order of frequency or wavelength

  
• Regions of the electromagnetic spectrum

  • Radio waves
  • Microwaves
  • Infrared waves
  • Visible light
  • x-ray
  • Ultraviolet radiation

  
• Radio waves


  • Longest of all electromagnetic waves, ranging from 10-1 m to 104 m
  • Frequency range from 30 kHz to 3000 MHz
• Radio wave frequency bands

  • Low frequency
  • Medium frequency
  • High frequency
  • Very high frequency
  • Ultra-high frequency
• Radar


  Radio detection and ranging, makes use of radio waves for detection of objects, weather forecasting, military surveillance, and air traffic control as well as monitoring speed in highway patrol and tracking satellites and debris
• Technologies that make use of radio waves


  • Automatic doors
  • Wi-Fi
  • Bluetooth
  • GPS
  • RFID
• Microwaves


  High-frequency radio waves, wavelength corresponding to 10-3 m to 10-1 m
• Uses of microwaves


  • Long-distance telephone calls
  • Cable television signals
  • Video or audio feeds from production vans to broadcast stations
  • Remote sensing for disaster management and mapping
  • Weather forecasting
  • Microwave ovens
  • Microwave ablation for shrinking or destroying tumors
  • Microwave imaging for monitoring breast cancer treatment
• Infrared waves

  Electromagnetic radiations with frequencies ranging from 3 × 1011 Hz to 4 × 1014 Hz, and wavelengths ranging from 7.5 × 10−7 to 10−3 m

  
• Uses of infrared waves


  • Remote controls
  • Burglar alarm systems
  • Night vision cameras
  • Certain types of thermometers
  • Transferring and printing data wirelessly
  • Cooking food
  • Healing sports injuries
  • Medical infrared imaging
• Visible light

  Electromagnetic radiations in the range of 4 × 1014 Hz to 8 × 1014 Hz with corresponding wavelengths of 4 × 10−7 m to 8 × 10−7 m

  
• Colors of visible light

  • Red
  • Orange
  • Yellow
  • Green
  • Blue
  • Indigo
  • Violet
• Laser


  Light amplification by stimulated emission of radiation, used in many medical procedures and biomedical research
• Ultraviolet radiation

  Electromagnetic radiations with frequencies ranging from 8 × 1014 Hz to 1017 Hz, and wavelengths ranging from 6 × 10−10 to 4 × 10−7 m

  
• Types of ultraviolet radiation

  • UVA
  • UVB
  • UVC
• Uses of ultraviolet radiation


  • Detecting forged bank notes
  • Forensic investigations
  • Sterilizing medical equipment and purifying water
  • Pest control
  • Producing "glow in the dark" effect
  • Treating skin conditions like psoriasis and vitiligo
• UVB

  Ultraviolet radiation from 280 nm to 314 nm
• UVC


  Ultraviolet radiation from 279 nm to 60 nm, almost completely absorbed by the atmosphere and does not reach the Earth's surface
• UVA


  Ultraviolet radiation that accounts for 95% of the solar UV reaching the Earth
• A major source of ultraviolet rays is the sun. Special lamps also emit UV rays.
• Uses of UV light


  • Detecting forged bank notes
  • Forensic investigations
  • Sterilizing medical equipment and purifying water
  • Pest-control devices and fly traps
  • Producing "glow in the dark" effect in theaters
• UVA


  Used to treat skin conditions like psoriasis and vitiligo that cause depigmentation of parts of the skin
• UVB and UVC


  Filtered by the ozone in the atmosphere
• UV stimulates the production of vitamin D in our body
• x-rays


  Also called Roentgen rays, discovered by German physicist Wilhelm Conrad Roentgen
• Soft X-rays


  Can penetrate soft substances like flesh and bones
• Hard X-rays


  More penetrating than soft X-rays, used mainly in industries
• Uses of X-rays


  • Detecting abnormalities in the skeletal system like fractures and tumors
  • Dental imaging
  • Computer axial tomography (CAT)
  • Airport security checks
  • Studying the arrangement of atoms in a crystal by diffraction
• Gamma rays


  Given off by radioactive materials like cobalt-60 and cesium-137, highly penetrating due to their very short wavelengths
• Uses of gamma rays


  • Detecting cracks in metals
  • Sterilizing equipment and commercial products
  • Controlling volume levels, density, and thickness in industries
  • Killing bacteria, insects, and parasites in food
  • Breeding new seed varieties with higher yields in agriculture
  • Eradicating pests like fruit flies
  • Destroying cancer cells in radiotherapy
• Electromagnetic radiation


  Can penetrate and affect us, seriously compromising our health and disturbing our environment
• Ionizing radiation


  Has sufficient energy to induce ionization, can cause immediate effects like death or radiation burns, and delayed effects like cancer or mutation
• Non-ionizing radiation


  Includes the other parts of the electromagnetic spectrum, although considered less dangerous than ionizing radiation, still poses some health issues
• Negative effects of electromagnetic radiation on humans

  • Interference with pacemakers
  • Cataracts from microwaves
  • Burns and pain from infrared waves
  • Eye damage from visible light, especially blue region
  • Blindness from lasers
  • Flash blindness from sudden bursts of intense light
  • Skin burns and cancer from ultraviolet rays