Physics 1E- Cooking and communication using waves

Physics 1E- Cooking and communication using waves

1. Uses of electromagnetic Radiation

   • Mircowaves
     • Microwaves have multiple uses: satellite communication, mobile phones, radars and heating materials
     • They are absorbed by water and fat molecules
     • They can penetrate about 1cm into food
     • Can cause burns when absorbed by body tissues
     • Can travel through glass and plastics
     • Are reflected by shiny metal surfaces
   • Infra-red
     • Are used to heat materials (in cooking) and in remote controls
     • They are used to heat the surface of the food in cooking
     • Reflected off shiny surfaces
     • They are absorbed by black objects

2. Transferring Energy

   • Microwaves
     • Are absorbed by water and fat molecules in the outside of the food
       • This increases the kinetic energy of the particles
       • The energy is transferred to the centre of the food by conduction and convection
   • Infra-red
     • Infra-red is absorbed by all of the particles on the top layer of the food
       • This increases the kinetic energy in the particles
       • Energy is then transferred to the centre by conduction and convection
   • The amount of energy in both waves depends on frequency and this also alters how dangerous it could be

3. Microwaves

   • Transmit information over large distances that are in line of sight
     • This is why mobile phone signal may cut out
   • The wavelength used in mobile phones isn't the same as the ones used in micro-wave ovens
   • Health concerns
     • Some people think constant use of mobile phones can increase ear and brain tumours
     • Children would be more at risk due to having thin skulls
     • The risk is increased if the mobile phones are used frequently
     • There is also concern about phone transmission masts
     • Scientists often publish conflicting evidence about studies such as mobile phone safety
       • In this case it is upto the public to decide about their own phone and whether they live near a phone mast

4. Microwave signals

   • Affected by:
     • Large obstacles such as trees and moutains
       • The signal doesn't diffract well
     • Poor weather conditions
     • Large areas of surface water
     • The curvature of the Earth
     • Interference between signals
   • Problems reduced by:
     • Limiting distance between transmitters
     • Positioning masts high on top of hills and/or tall buildings