Electromagnetic Spectrum

• Sir Isaac Newton proposed hat light was made of tiny particles known as the photons.
• The electromagnetic spectrum is divided into different regions based on wavelength or frequency, including radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.
• Electromagnetic waves or EM waves are transverse waves

  consisting of a combination of oscillating electric and

  magnetic fields.

  • EM wave is a combination of two waves – an electric wave and a magnetic wave.
  • EM waves do not require a medium to travel.
• In 1864, James Clerk Maxwell developed a theory to explain the basic nature of electromagnetic waves (Maxwell's equations)
• In 1887, Heinrich Hertz experimentally verified Maxwell's predictions with the production and detection of radio waves in his lab.
• In 1901, Marconi demonstrated long-range radio wave transmission between Britain and Newfoundland.
• In 1906, Reginald Fessenden (canadian) produced the first modulated radio transmission with voice and music.
• James Clerk Maxwell

  • Hypothesized that a changing electric field would produce a magnetic field.
  • Calculated the speed of light and concluded that light and other electromagnetic waves consist of fluctuating electric and magnetic fields.
• Maxwell's Theory

  • Electricity and magnetism were originally though to be unrelated.
  • Showed a close relationship between all electric and magnetic phenomena and proved that these play  symmetric roles in nature.
• Radio waves are the region in the EM spectrum with the longest wavelength and the lowest frequencies in the EM spectrum.
• A microwave is a form of electromagnetic radiation/waves with frequencies that range between 300 MHz (or 0.3 GHz) and 300 GHz (of wavelength from 1 mm to 1m long) or more.
• Microwaves

  • used for telecommunications
  • used to make a special conductor made of copper called chalcopyrite.
  •  used by fixed traffic speed cameras, they are used for the radar that is used by the ships, the aircraft and they are used in the weather forecasts as Doppler radar.
  • very useful in medicine as an alternative to the surgery.
• Infrared

  • wavelength just greater than that of the red end of the visible light spectrum but less than that of microwaves. Infrared radiation has a wavelength from about 800 nm to 1 mm, and is emitted particularly by heated objects.
• Thermography is used to determine the relative temperature of objects by detecting amounts of radiation it produces.
• Missiles are sent out to follow their targets based on their infrared radiation.
• Infrared technology is used to determine water temperature, map cloud, patterns, and make weather predictions.
• Visible Light

  • Light or "visible light" refers to the visible region of the electromagnetic spectrum – that is, the range of wavelengths that trigger brightness and color perception in humans. It lies between UV and infrared radiation.
• UVC (200-280 nm)

  • shortest wavelength
  • absorbed by the atmospheric ozone
  • disinfecting water, sterilizing surfaces, destroying harmful micro-organisms in food products and in air.
• UVB (290 nm to 320 nm)

  • has largest effect on the top layer of the skin

  • primarily responsible for sunburn, aging of the skin, and the development of skin cancer

  • allows the synthesis of vitamin D3, which helps to absorb calcium.
• UVA (320 nm to 400 nm)

  • longest wavelength

  • reaches deep into the layers of skin causing aging/wrinkling

  • regulate behaviors such as feeding, diurnal movement, mating and similar activities
• X-rays

  • an electromagnetic wave of high energy and very short wavelength, which is able to pass through many materials opaque to light. 
• Wilhelm Conrad Röntgen a German mechanical engineer and physicist, who, on 8 November 1895, produced and detected electromagnetic radiation in a wavelength range known as X-rays or Röntgen rays.
• A gamma ray, or gamma radiation, is a penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and so imparts the highest photon energy.