Cheesy Waves

Microwaves in a microwave oven are the kind of waves that don't travel anywhere but just stay in one place. These are called standing waves. You can make standing waves with a skipping rope or by banging a drum. In this experiment you can see standing waves by melting cheese in a microwave oven. Plus of course afterwards there is the added bonus of eating it!

You will need:

• A microwave oven


• Some slices of processed cheese


• A (microwaveable) plastic tray

What to do:

Remove the turntable from the microwave.
Lay strips of cheese on the tray and put it into the oven.
Either give it a quick blast (about 10 sec) on high power or try leaving it in there for 1 min on a low setting like defrost. (This is better if your microwave timer doesn't have seconds on it).
Take the tray out of the oven and look to see where the cheese has melted. The places where the cheese has melted show where the microwaves inside the oven are biggest (where the waves have maximum amplitude).

What's going on?

In some parts of the oven, the waves have a high amplitude and the cheese gets hot and melts. In other parts, the amplitude is small, or zero, and the cheese doesn't melt.
This is why you need a turntable in a microwave oven. If the food isn't turned round it doesn't get cooked evenly all over.
(I did this experiment in the microwave in the staff room and saw parts where the cheese didn't melt!)