E-learning powerpoint

1. ELECTROMAGNET
IC SPECTRUM

2. Objectives
 Describe the 7 main components of the
electromagnetic spectrum
 State the properties of electromagnetic waves
(EM wave)
 State the applications of electromagnetic
waves

3. 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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Goggles

5. How is electromagnetic waves
form?
 Created by accelerating electric charges,
moving the charges back and forth
 Produce oscillating magnetic and electric field

6. 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.

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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.

14. 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.