Microwaves are a low frequency wave with a wavelength of a few cm. They are used in mobile phones, TV signals, bluetooth and microwave ovens.
We looked at how microwaves are used in communications in the radio waves section so in this section we will focus on how microwave ovens work.
Microwave ovens use microwaves of a particular frequency, this specific frequency is the one that makes water molecule vibrate.
Microwaves are sent out from a source and reflected off the walls of the microwave. These echos interfere with each other until there is a standing wave: points of really high intensity and points of really low intensity within the microwave.
At these maximum points, which will be a wavelength apart, the water molecules will vibrate a lot and gain energy. This heat energy will be passed through the food by conduction but there would be points where the food was burnt or cold, if the plate didn't spin to help it.
Look at the animation on the right to see what happens.
We can use microwave ovens to measure the speed of light. Have a look at the experiment above.