ELECTROMAGNETIC WAVES SECONDARY 3 PHYSICS

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.

Electromagnetic Spectrum

• It is a group of different electromagnetic waves.

• There are 7 components in the spectrum.

Electromagnetic Spectrum

• Gamma rays

• X rays

• Ultraviolet

• Visible light

• Infra-red

• Microwaves

• Radio waves

Highest frequency Shortest wavelength Lowest frequency Longest wavelength

Uses of Gamma Rays

• Kill cancer cells

• Study the nucleus in atoms

Uses of X-rays

• Take pictures of bones in the body

• Study the crystal structure of crystalline substances

• Check for cracks in metal plates

Uses of Ultraviolet

• Detect counterfeit notes

• Gives the clothes a glow effect in discotheques

• Sun-tanning

• Sterilise medical equipment

Uses of Visible Light

• Enable us to see things

• Photosynthesis in plants

Uses of Infra-red

• Heating

• Haze photography

Uses of Microwaves

• Radar communication

• Analysis of the molecular and atomic structure

• Telephone communications

Uses of Radio Waves

• Radar communications

• TV and radio broadcasting

Common Properties of EM Waves

• All transverse waves

• All travel at the speed of light. (3 x 10 8 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