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^{– 7}m and 7.2 ×10^{– 7}m. 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):

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.