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The Concept of Electromagnetic Waves

Unlike mechanical waves, electromagnetic waves are waves that require no material medium for propagation. Thus, they can propagate through a vacuum or free space.

The human eye can only see light of which the wavelength lies between 3.8 ×10– 7m and 7.2 ×10– 7m. Other examples of electromagnetic radiation differ from visible light  only in wavelength and in the ways of producing them. However, they all have the same velocity of value 3.0 ×108m/s.

S/NElectromagnetic
Spectrum
Wavelength (m)Uses
1Radio waves10−3 to 103(i) Used in radar and cooking
2Infra-red10−6(i) Used for taking pictures in
the dark
(iii) To dry paint
(ii) For treating muscular
complaints.
3Visible light (red)7 × 10−7(i) For visibility (ROYGBIV)
Visible light (violet)4.5 × 10−7(ii) For visibility
4Ultra-violet10−8(i) They cause fluorescence
(ii) They cause sunburn
(iii) They affect photographic
plates.
5X-rays10−10(i) To destroy malignant growths
in the body
(ii) To locate broken bones
iii)To locate cracks in metal
castings, etc.
6Gamma-rays10−11(i) They cause fluorescence.

EVALUATION (POST YOUR ANSWERS USING THE QUESTION BOX BELOW FOR EVALUATION AND DISCUSSION):

  1. What are electromagnetic waves?
  2. Differentiate electromagnetic waves from mechanical waves.
  3. What is the common speed value of all electromagnetic waves?
  4. List the components in the electromagnetic spectrum.
  5. What is the wavelength range of the radio waves?
  6. Mention two uses of the x-rays.

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