electromagnetic spectrum

Question 1

What are electromagnetic waves?

Answer 1

• Electromagnetic waves are made up of oscillating electric and magnetic fields
• all electromagnetic waves are transverse waves. This means that the electric and magnetic fields oscillate perpendicularly to the direction of propagation of the electromagnetic waves

Question 2

Properties of electromagnetic waves

Answer 2

• They do not carry electric charges
• they can travel without a medium, with the same speed of a 3.0 x 10^8 m/s in a vacuum
• when an electromagnetic wave travels from one medium to another, only its speed and wavelength change. Its frequency, which depends only on the source of the wave, does not change
• they undergo reflection and refractions
• they transfer energy

Question 3

Wave speed equation

Answer 3

Speed of the wave in any medium m/s = frequency of wave Hz x wavelength of the wave m

Question 4

Electromagnetic spectrum

Answer 4

From left to right: wavelength decreases, frequency increases
Radiowaves, microwaves, infrared, visible light, ultraviolet radiation, X-rays, gamma rays

Question 5

Uses of radio waves

Answer 5

• Television and radio communication
• radio telescopes for radio astronomy to study radio frequencies from outer space
• radio frequency identification tag for tagging library books, items in warehouses and merchandise in shops

Question 6

Uses of microwaves

Answer 6

• Microwave oven
• WiFi signals
• mobile phone communication
• Global Positioning System (GPS)
• satellite communication

Question 7

Uses of infrared radiation

Answer 7

• Remote control
• intruder alarm
• thermal imaging
• infrared thermometer

Question 8

Uses of visible light

Answer 8

• Photography
• optical fibers in medicine and telecommunication

Question 9

Uses of ultraviolet radiation

Answer 9

• Sterilization of medical equipment
• Disinfection of water in water treatment plants
• sunbed for artificial tanning
• Check for counterfeit bank notes

Question 10

Uses of X-rays

Answer 10

• Medical radiology: radiography to produce X- ray imaging to diagnose fractured bones or tooth decay. Radiation therapy to treat cancer
• industrial radiology: scan for manufacturing defeats in metal parts
• scan luggage for prohibited items at airports

Question 11

Uses of gamma rays

Answer 11

• medical radiology: gamma imaging, radiation therapy to treat cancer
  -Industrial radiology: scan for manufacturing defects in metal part
• sterilization of medical equipment
• sterilization of food

Question 12

Hazardous effects of microwaves and infrared radiation

Answer 12

Heating effect (temperature increases)

Question 13

Hazardous effects of ultraviolet radiation

Answer 13

• Prolonged exposure to UV radiation can lead to sunburns, premature aging and increased risk of skin cancer
• UV radiation can be ionising

Question 14

Hazardous effects of X-rays and gamma rays

Answer 14

• ionising radiation (radiation that has the energy to remove electrons from atoms or molecules, thereby ionising them)
• exposure to ionising radiation can damage biological molecules, living cells and tissues. it can lead to cell death, mutations and abnormal cell division
• this may cause cancers such as leukemia and/or deformities to a developing foetus