Electromagnetic Spectrum

The Spectrum

• A continuous spectrum of waves
• One end: high frequency and short wavelength
• The other end: low frequency and long wave length

All the waves have these properties:

• They transfer energy
• Transverse waves
• Travel at the speed of light (300 000 000 m/s)
• Can all be reflected, refracted and diffracted

The spectrum can be divided into groups which have different properties because of the wavelength and frequency. All the different groups have different uses and sources.

Radio Waves: The sources are radio transmitters and TV transmitters and the uses are long-, medium-, and short-wave radio, TV

Microwaves: The sources are microwave transmitters and ovens (and microwaves) and the uses are mobile phone and satellite cmmunication, cooking

Infra-red: The sources are hot objects and the uses are infra-red cookers and heaters, TV and Stero remote controls and night vision

Visible Light: The sources are luminous objects and the uses are for seeing, communication, optical fibres and photography

Ultraviolet: The sources are UV lamps and the sun and the uses are fluorescent tubes and UV tanning lamps

X-Rays: The sources are X-rays and the uses are X-Radiography

Gamma Rays: The sources are radioactive materials and the uses are sterilising food and equipment and food. and radiotherapy.

The waves further down the spectrum have a higher frquency and shorter wavelength.

Digital

• Information is converted into a sequence of numbers called binary code which consist of just two numbers: 0 and 1.
• These numbers are then converted into a series of electical pulses.

Analogue

• Information is converted into electrical voltages or currents that vary continuously.

Advantages of using Digital

• Carry more information
• Maintain quality
• Noise can be ignored
• Use optical fibres