試題詳解

8. A star radiates uniformly in all directions. At a distance of 5.0 ✖ 10¹² m from the star, the intensity of the radiation from the star is 15 W / m₂ . What is the total power output of the star?
(A)   3.2✖10³⁸W
(B) 4.7✖10 ²⁷W 
(C)  3.8✖10²⁶ W
(D)  7.5✖10¹³W  
(E)   1.1✖10¹⁵W