Cooking with Waves
- Infrared (non-ionising waves that produce heat) radiation does not penetrate food easily.
- Microwaves (non-ionising waves used in satellite and mobile phone networks- also in microwave ovens) penetrate up to 1cm of food.
- Microwaves can penetrate glass or plastic. They are reflected by shiney metal surfaces.
- Special glass in a microwave oven door reflects microwaves.
- They can cause body tiddue to burn.
1 of 5
- Energy is transferred by waves:
- The amount of energy depends on the frequency or wavelength of the wave.
- High frequency waves transfer more energy.
- Normal ovens cook by infrared radiation:
- Energy is absorbed by the surface of the food.
- The kinetic energy of the surface food particals increases.
- The rest of the food is heated by conduction.
- Microwave ovens cook food by microwave radiation:
- The water or fat molecules in the outer layers of the food vibrate more.
2 of 5
- Microwaves have wavelengths between 1mm and 30 cm.
- Mobiles use longer wavelengths than microwave ovens.
- Less energy is tranferred by mobile phones.
3 of 5
- Microwave radiation is used to communicate over longer distances.
- The transmitter and reciever must be in line of site.
- Aerials are usually on top of high buildings.
- Satellites are used for microwave communication.
- The signal from the Earth is recieved, amplified, and re-transmitted back to Earth.
- Satellites are in line of sight becuse there are no obstructions in space.
- Large aerials can handle thousands of phone calls and television channels at once.
4 of 5
Microwave Communication 2
- There are concerns about the use of mobile phones and where phone masts are situated.
- Scientists publish studies of their findings so others can check their findings.
- Signal strength of mobile phones can change over longer distances.
- Microwaves do not show much diffraction (the spreading out of a wave when it passes through a gap or around an edge.)
- Bad weather conditions and large areas of water can scatter the signals.
- The shape of the Earth limits the line of site so transmitters have to be on tall buildings or close together.
- Mobile phones can interfere with sensitive equiptment:
- They are banned on planes and in many hospitals.
5 of 5