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.
|1||Radio waves||10−3 to 103||(i) Used in radar and cooking|
|2||Infra-red||10−6||(i) Used for taking pictures in|
(iii) To dry paint
(ii) For treating muscular
|3||Visible light (red)||7 × 10−7||(i) For visibility (ROYGBIV)|
|Visible light (violet)||4.5 × 10−7||(ii) For visibility|
|4||Ultra-violet||10−8||(i) They cause fluorescence|
(ii) They cause sunburn
(iii) They affect photographic
|5||X-rays||10−10||(i) To destroy malignant growths|
in the body
(ii) To locate broken bones
iii)To locate cracks in metal
|6||Gamma-rays||10−11||(i) They cause fluorescence.|
EVALUATION (POST YOUR ANSWERS USING THE QUESTION BOX BELOW FOR EVALUATION AND DISCUSSION):
- What are electromagnetic waves?
- Differentiate electromagnetic waves from mechanical waves.
- What is the common speed value of all electromagnetic waves?
- List the components in the electromagnetic spectrum.
- What is the wavelength range of the radio waves?
- Mention two uses of the x-rays.
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