A plane wave with amplitude $A$ falls on a surface of area $S$, arranged so that it is perpendicular to the wave’s direction of travel. The rate at which energy reaches the surface is $E$. The wave amplitude is then raised to $2A$, while the surface area is reduced to $\tfrac{1}{2}S$. What energy per unit time reaches this smaller surface?
- A$4E$
- B$2E$
- C$E$
- D$\tfrac{1}{2}E$