Uses of Electromagnetic Waves: Notes for Electronics Engineering pdf ppt

Uses of Electromagnetic Waves:

Introduction:

  • Wavelength of the ElectroMagnetic spectrum continually changes
  • high frequency = short wavelength
  • high frequency = high energy
  • high energy = more dangerous

Radio Waves (communications):

  • TV and FM radio (short wavelength)
  • Direct line of sight with transmitter (do not diffract)
  • Medium wavelength – travel further because they reflect from layers in the atmosphere

Satellite signals (Microwaves):

  • Frequency of microwaves pass easily through atmosphere and clouds

Cooking (Microwaves):

  • Microwaves are absorbed by water molecules.
  • These water molecules become heated > heat food
  • Dangers: microwaves are absorbed by living tissue Internal heating will damage or kill cells

Infrared Radiation (remote controls, toasters)

  • Any object that radiates heat radiates Infrared Radiation
  • Infrared Radiation is absorbed by all materials and causes heating
  • It is used for night vision and security cameras as Infrared Radiation is visible in daytime or night-time
  • Police use it to catch criminals, army use it to detect enemy
  • Dangers: damage to cells (burns)

Ultraviolet:

  • Dangers:
    • overexposure to UVA and B damaged surface cells and eyes and can cause cancer.
      • There is a problem with current sunscreens which protect against skin burning from high UVB but give inadequate protection against free radical damage caused by UVA.
      • Dark skins are not necessarily safer from harm.
      • Sun exposure for the skin is best restricted to before 11am and after 3pm in the UK in summer months.
  • Benefits:
    • sanitary and therapeutic properties have a marked effect on architecture, engineering and public health and have done so throughout history.
    • UVC is germicidal, destroying bacteria, viruses and moulds in the air, in water and on surfaces.
    • UV synthesises vitamin D in skin, controls the endocrine system and is a painkiller.
    • Used in state of the art air-handling units, personal air purifiers and swimming pool technology.
    • Used to detect forged bank notes: they fluoresce in UV light; real bank notes don’t. Used to identify items outside visible spectrum areas, known as ‘black lighting’.

X-rays:

  • X-rays detect bone breaks
  • X-rays pass through flesh but not dense material like bones
  • Dangers: X-rays damage cells and cause cancers. Radiographer precautions include wearing lead aprons and standing behind a lead screen to minimise exposure

Gamma Rays:

  • Gamma Rays cause and treat cancers
  • In high doses, gamma can kill normal cells and cause cancers
  • Gamma can be used to kill mutated cells though too.

 

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One thought on “Uses of Electromagnetic Waves: Notes for Electronics Engineering pdf ppt

  • 10/01/2018 at 4:11 PM
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