9. How do microwave ovens work?
• Microwaves are produced by a magnetron
• Reflected by metal on the inside of the oven
• Absorbed by the food
• Not very good absorption so they go through
the food rather than be absorbed by the
surface
20. Questions
• Light, long-wavelength infrared, short-
wavelength infrared
• Which of the above:
– Can be detected by the human eye?
– Can pass through glass?
– Is emitted by red hot objects?
21. Questions
• Explain why a metal bar starts to glow red when
it is heated up
• Infra-red has a heating effect on most solids.
What does this tell you about whether this
radiation is reflected, transmitted or absorbed
• A TV remote control emits an infrared beam that
carries coded information to the TV set. Explain
how you might use this to find out which
everyday material absorb infrared and which
transmit it.
• List three uses of microwaves.
