Why Don’t the Waves Leak Out the Door?

Why don’t the waves leak out the door?

Remember, one wave is 12.2 cm long. Inside the door glass is a metal sheet full of tiny holes, about 1 to 2 mm across. To the waves, those holes are far too small, so they bounce back. But light, whose waves are tiny (the yellow dots), passes through the holes and reaches your eyes. That is how you can see inside while the waves stay trapped.

Why?A big ball can’t get through a fine net, but grains of sand pour right through. The microwaves are the ball and light is the sand. A light wave is about half a thousandth of a millimeter long, so to light these holes are wide-open windows.

Learn moreBy calculation, after passing through a 1 mm sheet with 1.5 mm holes, the waves are about 136 times weaker. Real doors add a seal around the edge that cuts the leakage even further. That is why you should never use a microwave with a broken door.

Hole in the door’s metal screen (example)

1.5 mm

textbook formulas · example oven cavity 31.5 × 21 × 32.5 cm