if the distance between a point soutce of light and a surface is tripled,the intensity if
if the distance between a point soutce of light and a surface is tripled,the intensity of illumination on the surface will be
a,tripled
b,doubled
c,reduce to1/2
d,reduce to1/3
e,reduce to1/9
想问一下,这题有公式吗?为什么选E