Final answer:
Doubling the length of a fin on a heat sink does not double the heat transfer rate. The rate of heat transfer is determined by the surface area, which increases by a factor of four when the length is doubled.
Step-by-step explanation:
When the length of a fin on a heat sink is doubled, the heat transfer rate from the fin does not double.
The rate of heat transfer is determined by the surface area of the fin, and the area is the product of two spatial dimensions.
When the length is doubled, the surface area increases by a factor of four, not two.
This means that the heat transfer rate will increase by a factor of four, not two.