Explain why cookies baked near the turned up edges of a cookie sheet receive more energy than those...?

Question

baked near the center.

Answer 1

1. They could be thinner
2. The outside has to be warmed up before the inside.
3. They have more exposed surface area so they can absorb more heat.

Actually 3 is the reason for 2. To reach the center of an object the heat radiation has to warm up the exterior. This means there is a temperature difference with the exterior almost always hotter. This is why you stick a knife into the center of a pie to see if it is finished cooking. If the knife comes out clean then the pie is done.

Microwaves work by increasing the vibration of the molecules inside the object. By this theory the heating should be more uniform, but the object being heated shields the interior against more of the microwave radiation. Also different materials heat at a different rate under a microwave. The process also can create hot spots if the microwave generator is not uniform. This is common enough that most microwaves have a rotating plate to allow for it.

Answer 2

Reflection of heat off the edges of the cookie sheet cause the outer cookies to get more heat than the inner cookies.