ELECTROMAGNETIC SPECTRUM

Objectives

Describe the 7 main components of the electromagnetic spectrum

State the properties of electromagnetic waves (EM wave)

State the applications of electromagnetic waves

What are Electromagnetic waves? Consist of 7 components

Radio waves Microwaves Infra-red radiation Visible light Ultra-violet waves X-rays Gamma rays

105 m

10-14 m

Wavelength

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How is electromagnetic waves form?

Created by accelerating electric charges, moving the charges back and forth

Produce oscillating magnetic and electric field

Electromagnetic Waves

Electromagnetic spectrum is continuous. No distinct boundaries between each

component. Gamma rays have the shortest

wavelength and highest frequency. Radio waves have the longest

wavelength and lowest frequency.

Properties of Electromagnetic waves

Transfer energy from one place to another

They are transverse waves Travel through vacuum with the speed of

light (3 x 108 m s-1)

Show wave properties like reflection and refraction

Obey wave equation v = fλ

Application of Electromagnetic waves

Radio waves (10-1 to 105) Longest wavelengths Able to go around obstructions due to

their long wavelength Used in radio broadcasting,

telephone transmission, television, radar, navigation system

Microwaves (10-3 to 10-1) Microwave oven – cause the water

molecules in the food to vibrate. The vibration causes friction at a molecular level which will heat up the food.

Satellite communication and television – signals are transmitted through aerial dishes to satellites in the space.

Application of Electromagnetic waves

Infra-red Radiation (10-7 to 10-3) All object emit infra-red radiation We experience infrared-radiation in the form of

heat Ear thermometer: measure the amount of infra-red

radiation that emanates from the eardrum. Used in remote controls for electronic devices and

infra-red motion detectors.

Application of Electromagnetic waves

Visible Light (10-7) Only part of the EM spectrum that can be

detected by human eye. Wavelength: 700nm (red) to 400nm (violet) Laser can be used in industries

to weld metals together and in medicine.

Optical fibres in telecommunications

Application of Electromagnetic waves

Application of Electromagnetic waves

Ultra-Violet (UV) Radiation (10-8 to 10-

7) Sunlight is the main source of UV

radiation Ultraviolet lamps are used in sunbeds for

artificial tanning. Used in hospital for sterilisation - kill

bacteria and viruses

Application of Electromagnetic waves

X-Rays (10-13 to 10-8) used to produce the X-ray images to

examine a person’s body or tooth decay used in X-ray scanners in airports can penetrate through all materials

except lead.

Application of Electromagnetic waves

Gamma Rays (10-14 to 10-10) It can be used to treat cancer by killing

cancer cells. Cause serious damages to living tissues.