Question

percy l. spencer accidentally discovered the heating capacity of ____ during his observation with the power tube that drives a radar set.
answer input:
spelling counts but capitalization doesnt.

Explanation:

Percy L. Spencer is known for accidentally discovering that microwaves (electromagnetic waves in the radar - related power tube) can heat food. He noticed that a candy bar in his pocket melted while he was working with the radar - related power tube, which led to the development of the microwave oven. So the heating capacity he discovered was of microwaves.

Answer:

microwaves