Q2

• Electromagnetic wave


  A disturbance that carries energy and can pass through a medium
• Electromagnetic Spectrum


  A continuum of electromagnetic waves arranged according to frequency and wavelength
• Electromagnetic waves in order

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


  • Have the longest wavelengths of all the electromagnetic waves
  • Range from around a foot long to several miles long
  • Used to transmit data and for radio and television communication
• Microwaves


  • Shorter than radio waves with wavelengths measured in centimeters
  • Used to cook food, transmit information, and in radar
• Infrared


  • Between microwaves and visible light
  • Near infrared used in TV remotes
  • Far infrared are thermal and give off heat
• Visible light


  • Wavelengths range from 700nm (red) to 400nm (violet)
  • Separated into constituent colors when passing through a prism
• Ultraviolet


  • Have shorter wavelengths than visible light
  • Cause sunburns
  • Blocked by the ozone layer
• 1. rays


  • Have even shorter wavelengths than ultraviolet
  • Can penetrate soft tissue
  • Used to take X-ray pictures of bones
• Gamma rays


  • Shortest waves in the spectrum with the most energy
  • Used in treating cancer and taking detailed diagnostic images
  • Produced in high energy nuclear explosions and supernovas
• Microwaves can penetrate the atmosphere of the earth
• Satellite communication using microwaves

  1. Microwaves transmitted by antenna to satellite

  2. Satellite amplifies and re-transmits signal to other antenna
• Cell phone communication using microwaves

  1. Information transformed into signals

  2. Signals sent through microwaves to nearest cell tower

  3. Signal transmitted to intended destination device
• Radar using microwaves


  1. Device sends out short burst of microwaves

  2. Microwaves reflect off vehicle

  3. Reflected signal detected to compute vehicle speed
• Ultraviolet rays


  • Germicidal in nature, destroy bacteria, viruses and molds
  • Used to detect forged bank notes
  • Used to sterilize water
  • Produce vitamin D in skin and cause tanning
  • Can be harmful, cause skin cancer
• 1. rays


  • Long wavelength can penetrate flesh but not bones, used to diagnose fractures and tumors
  • Short wavelength can penetrate metal, used to inspect welded joints
• Infrared


  • Emitted by all objects, amount and wavelength depend on temperature
  • Differences in color indicate differences in temperature
  • Used in infrared remote controls
• Microwave oven


  Food absorbs certain microwave frequencies strongly<|>Microwaves agitate water molecules, creating friction that produces heat to cook food
• Gamma rays


  • Can cause and also treat cancers
  • High dose kills normal cells causing cancer, proper amount can kill mutated cells
• Radio frequency radiation absorbed in large amounts can damage DNA and cause cancer
• Microwave radiation can heat body tissue, eyes and testes are particularly vulnerable
• Infrared radiation is sensed as warmth on the skin
• Visible light can cause erythema, pigmentation, thermal damage and free radical production
• Ultraviolet rays can cause sunburns, premature skin aging, eye problems like corneal inflammation and cataracts
• 1. rays can cause DNA mutations and lead to cancer, higher doses can cause skin redness, infertility, cataracts, and hair loss
• Gamma rays can penetrate matter and change DNA, produced by hottest and most energetic objects in the universe
• Infrared


  Infrarrojo
• Infrared are used in TV remote controls
• Speed gun uses microwaves to calculate speed of moving vehicle
• Microwave can cook food
• Cell phones use microwaves to communicate
• Forged bank notes can be detected through UV light
• The human eye cannot detect gamma rays
• 1. ray is not safe for pregnant women
• Radiation is all around us
• Large dose of gamma rays can be used to treat cancer
• Human can sense infrared through warmth