A. Light CAN travel through a vacuum. It is an electromagnetic transverse wave, and thus needs no medium.
Answer:
Both warming up and cooling down or not important
Optic fiber is the medium that is often used to transfer computer information
Answer:
80%
Explanation:
The thermal energy output by the oven is 800 J which is the useful energy that can be utilized for cooking.
The electrical energy input to the oven is 1000 J.
The efficiency of the oven =
(Useful energy output)/(Total energy input to the oven) x 100

Hence, the efficiency of the oven is 80%.