Analysing Electromagnetic Waves

Analysing Electromagnetic Waves

Analysing Electromagnetic Waves

  1. The electromagnetic spectrum consists of a group of waves of similar nature. The members of the electromagnetic spectrum arranged in increasing frequencies (decreasing wavelengths) are radio waves, microwaves, infrared rays, visible light, ultraviolet rays, X-rays and gamma rays.
  2. Electromagnetic waves are joint electric and magnetic fields which can travel through space with no need of a medium to carry them. Figure shows the representation of electromagnetic waves.
    Analysing Electromagnetic Waves 1
  3. All the members of the electromagnetic spectrum
    (a) transfer energy from one place to another
    (b) are transverse waves
    (c) can travel through a vacuum
    (d) travel with a speed of 3 x 108 m s-1 in a vacuum

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The Electromagnetic Spectrum

Table lists out the sources, characteristics and applications of the electromagnetic spectrum.

Type and wavelengthsSourcesCharacteristicsApplications
Radio waves
λ : 103 — 10-1 mThe Electromagnetic Spectrum
  • Radio
  • Television transmitter
  • Carry audio and visual information
  • Broadcasting and wireless communication
  • UHF (ultra high frequency) radio waves – TV and mobile phones
  • VHF (very high frequency) radio waves – local radio and wireless communication used by policemen
Microwaves
λ : 10-1 – 10-3 m

The Electromagnetic Spectrum 1

  • Radar transmitter
  • Microwave ovens
  • Can penetrate the atmosphere
  • Suitable for satellite communication
  • Can excite water molecules, therefore suitable for cooking
  • Communication with satellites
  • Used in radar systems
  • Global Positioning System (GPS)
  • For cooking – microwave ovens
Infrared rays
λ : 10-3 – 10-6 m

The Electromagnetic Spectrum 1

  • Warm or hot objects
  • The Sun
  • Also known as infrared radiation
  • When an object absorbs infrared rays, it becomes hotter
  • For cooking food – ovens, grills and toasters
  • Remote controls for televisions and video players
  • Intruder alarm systems
  • Night vision
Visible light
λ : 8 x 10-7 – 4 x 10-7 mThe Electromagnetic Spectrum 3
  • The Sun
  • Hot objects
  • Electric bulbs Fire
  • LED
  • Consists of seven components (red, orange, yellow, green, blue, indigo and violet)
  • Photography
  • Photosynthesis by plants
  • Human and animal sight
Ultraviolet rays
λ : 10-7– 10-9 mThe Electromagnetic Spectrum 4
  • The Sun
  • Mercury lamps
  • Sparks
  • Very hot objects
  • Can be absorbed by glass and the ozone layer in the atmosphere of the Earth
  • A small amount is good for producing vitamin D in our skin while a large amount is bad for eyes and can cause skin cancer
  • Fluorescent lamp
  • Detection of security markings in currency notes
  • Sterilisation of surgical tools and plant seedlings
X-rays
λ : 10-9 – 10-11 mThe Electromagnetic Spectrum 5
  • X-ray tubes
  • Outer space bodies
  • High energy
  • High penetrating power
  • Very dangerous
  • Helps doctors to check bones and teeth
  • Helps engineers to check welds and metal joints
  • Kills cancerous cells
  • X-ray diffraction helps scientists to study the arrangement of atoms in various substances
  • To detect whether an art piece is genuine or not
Gamma rays
λ : 10-11 m or lessThe Electromagnetic Spectrum 6
  • Radioactive substances
  • Cosmic rays
  • High energy
  • High penetrating power
  • Very dangerous
  • Kills cancerous cells
  • Sterilisation of surgical tools and food
  • Helps engineers to check welds and metal joints

 

Detrimental Effects of Electromagnetic Waves

  1. The human eye cannot detect ultraviolet rays but an overexposure to these rays can cause blindness. Overexposure to ultraviolet rays can also cause sunburn and skin cancer.
  2. Due to the high energy associated with short wavelength radiations, ultraviolet radiations, X-rays and gamma rays can damage living tissues. These radiations ionise atoms and molecules in living cells. These cells may die or become cancerous.
  3. X-rays have very high penetrating power. These rays have adverse effects on living cells. Cancer and genetic defects can be induced by exposure to X-rays.
  4. Gamma rays have very high penetrating power. Exposure to gamma rays can lead to genetic defects and the harming of living cells.