Topic 5- light and the EMF

• At incident angles less than the critical, light is refracted.
• At incident angles greater than the critical, light undergoes Total Internal Reflection.
• At the critical angle light reflects and passes out at 90 degrees to the normal.
• The 'fatter' the lens, the more powerful it is.
• Converging lens-


  Image is real/positive.
• Diverging lens-


  Image is virtual/negative.
• As the Electromagnetic Spectrum progresses, the wavelength decreases, the frequency increases and the danger increases.
• Danger of microwaves-


  Internal heating of body cells.
• Danger of infrared-


  Skin burns.
• Dangers of UV-


  Damage to surface cells and eyes, leading to skin cancer and eye conditions. Cataracts not burns.
• Dangers of x-ray and gamma-

  Mutation leading to cancer.
• Uses of radio waves-

  Broadcasting, communication and low level satellite transmissions (150m).
• Uses of microwaves-


  Cooking, WiFi, communications and low level satellite transmissions. Speed cameras (150mm)
• Uses of infrared-


  Cooking, thermal imaging, short range communications, optic fibres, TV remote, security (900nm).
• Uses of visible light-


  Vision, photography, and illumination. Eyes only detect a limited range.
• Uses of UV-


  Security marking, fluorescent lamps, forged bank notes and disinfecting water.
• Uses of x-ray-


  Observing internal structure, broken bones, airport security, scanners and medical x-rays.
• Uses of gamma-


  Sterilising food and equipment, cancer detection and treatment.
• Radio waves can be produced or induced by oscillating free electrons in alternating electrical circuits.