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/N | Electromagnetic Spectrum | Wavelength (m) | Uses | |
| 1 | Radio waves | 10−3 to 103 | (i) Used in radar and cooking | |
| 2 | Infra-red | 10−6 | (i) Used for taking pictures in the dark (iii) To dry paint (ii) For treating muscular complaints. | |
| 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 plates. | |
| 5 | X-rays | 10−10 | (i) To destroy malignant growths in the body (ii) To locate broken bones iii)To locate cracks in metal castings, etc. | |
| 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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