4.6.2.4 Uses and applications of Electromagnetic Waves

Question 1

Uses of radio waves:

Answer 1

• TV and radio
• Local/national radios
  
  • as they have a low frequency and long wavelength and can travel far without losing quality
  • can travel many hundreds of km’s
• International radio
  
  • high freq. (up to 30MHz)
  • radio waves reflect off ionosphere

Question 2

Uses of microwaves:

Answer 2

• Satelite communication
  
  • can travel through the atmosphere
  • unlike other radio waves, they are not reflected by the ionosphere but are refracted a little and then pass into space
  • WiFi
• Cooking
  
  • water molecules absorb the wavelength of the wave - so thermal energy is transferred to the food from the wave

Question 3

Why do you get no ionising radiation exposure from a microwave oven?

Answer 3

• wavelength too large to pass through mesh on microwave door (light can move through the mesh - why you can see the food cooking)
• so microwaves cannot zap you through the microwave door

Question 4

Uses of X-rays and gamma rays:

Answer 4

• Medical imaging and treatments
  
  • very high in energy so can penetrate material easily
  • bones absorb X-rays
  • soft tissues do not absorb X-rays - lets X-rays pass be transmitted
• Treating cancer
• Security
• Crystallography
  
  • looking at crystals and the arrangement of atoms

Question 5

Uses of UV waves:

Answer 5

• energy efficient lamps, sun tanning beds
  
  • radiates the least heat but most energy
• fluorescence
  
  • response of atoms to UV rays
  • electrons emit visible light

Question 6

Uses of visible light:

Answer 6

• allows us to see objects
• high speed transmission of data - communications
  
  • fibre optic cables
  • best reflection and scattering in glass have too short/long wavelengths
  • total internal reflection
• lasers
• to look inside person
• see inside engines

Question 7

Uses of infrared:

Answer 7

• cooking food, infrared cameras
  
  • transfers thermal energy