Black Grating In The Microwave
There is no reason to take a close look at your microwave. However, you do not have to be super observant to see that black grating on the microwave door. Known as the Faraday shield, this stops the electromagnetic fields from getting out and then warming people! If that ever happens, you will be at risk AND the food is not going to get cooked. We do not know which one of these is worse.

Black Grating In The Microwave
Dimples On Golf Balls
The truth is that golf balls are not really round. Take a good look at them and you will see all those dimples on the surface of the ball. It turns out that golfers realized that balls with nicks and bumps often reach further distances than new ones. These imperfections make turbulence and reduce drag. The dimples were added for better lift.

Dimples On Golf Balls