1. ELECTROMAGNETIC WAVES
SECONDARY 3 PHYSICS

2. WHAT ARE EM WAVES?
Electromagnetic waves (EM waves for short) are waves that can travel in a vacuum.
These waves are created by the vibration of an electric charge.

3. Electromagnetic Spectrum
It is a group of different electromagnetic waves.
There are 7 components in the spectrum.

4. Electromagnetic Spectrum
Gamma rays
X – rays
Ultraviolet
Visible light
Infra-red
Microwaves
Radio waves
Highest frequency
Shortest wavelength
Lowest frequency
Longest wavelength

5. Uses of Gamma Rays
Kill cancer cells
Study the nucleus in atoms

6. Uses of X-rays Take ‘pictures’ of bones in the body
Study the crystal structure of crystalline substances
Check for cracks in metal plates

7. Uses of Ultraviolet Detect counterfeit notes
Gives the clothes a ‘glow’ effect in discotheques
Sun-tanning
Sterilise medical equipment

8. Uses of Visible Light
Enable us to see things
Photosynthesis in plants

9. Uses of Infra-red
Heating
Haze photography

10. Uses of Microwaves Radar communication
Analysis of the molecular and atomic structure
Telephone communications

11. Uses of Radio Waves
Radar communications
TV and radio broadcasting

12. Common Properties of EM Waves
All transverse waves
All travel at the speed of light. (3 x 108 m/s)
Can travel through solid, liquid, gas and vacuum
Obey the laws of reflection and refraction
All can be absorbed and emitted by matter
The wave equation is applicable to all