Question

How are a wave's energy and the wave's amplitude related?
A. Energy is one-half the amplitude
B. Energy is double the amplitude
C. Energy is the reciprocal of the amplitude
D. Energy is proportional to the square of the amplitude

Answer 1

Answer is D

http://www.physicsclassroom.com/class/waves/u10l2c.cfm


See link above and scroll down the to the part that reads \[E \ \alpha \ A^2\] (which is in red). This tells us that the energy E is proportional to the amplitude squared.