Light – An Electromagnetic Wave

• What is light?

  • has both wave and particle properties
  • Is made of discrete packets of energy called photons
  • Photons have no mass, and travel at the speed of light
• Speed of Light

  • Light and all forms of electromagnetic radiation travels at a very high speed
  • Speed of light = 3x10^8 = 300 000 000 m/s or 300 000 km/s
  • Does not need a medium to travel through
• • Light waves are called electromagnetic waves like water waves, it involves energy from one point to another
• • Electromagnetic waves (EM) are formed by vibrations of electric and magnetic fields
• What is Special about EM waves?

  They do not require a medium, the energy is transferred through radiation, meaning they can travel through space
• Electromagnetic Spectrum

  • Classification of all the different electromagnetic waves in order of the energy of the waves (and their wavelengths)
  • Travel at the speed of light regardless of wavelength
• Wavelength

  • The distance between successive crests of a wave 
  • From crest or trough to the next 
• • Smaller wavelengths carry more energy, higher frequency - higher energy means the wave can penetrate many objects and cause damage
• • Longer wavelengths carry less energy, lower frequency 
• Visible light

  • Whatever colour is not absorbed (detected) by the human eye is reflected. That is the colour we see 
• • ROY G BIV  
  • Red, orange, yellow, green, blue, indigo, violet
  • This is called the visible light spectrum ^^
  • Ranging from 700m (red) to 400m (violet)
  • Violet containing more energy than red light
• • White pigments reflect the entire visible spectrum into our eyes
• • Black pigments do not reflect any of the visible spectrum, energy is absorbed and converted into infrared energy (heat)
• • If not absorbed, it is reflected (the light we see)
• 1. Radio waves: broadcast radio, television
  2. Microwaves: cooking, radar telephone, other signals
  3. Infrared Light: transmits heat from sun, fires, radiators
  4. Visible light: makes things able to be seen, defected with human eyes, ROYGBIV, white light split into colours with its own wavelength
  5. Ultraviolet: absorbed by sun, used in fluorescent tubes
  6. X-rays: viewing inside of objects and bodies
  7. Gamma rays: medecin, killing cancer, produced radioactivity decay + by sun/stars, produced by nuclear weapons, 10^18 or higher