A point source kept at a distance of 1000 m has an illumination I. To change the illumination to 161, the new distance should become
A. 250 m
B. 500 m
C. 750 m
D. 800 m
Answer:A
A point source kept at a distance of 1000 m has an illumination I. To change the illumination to 161, the new distance should become
A. 250 m B. 500 m C. 750 m D. 800 m