Решение задачи по физике раздел 13 пункт 88 оптика

88. The parallel beam carrying a uniform luminous flux density j = 200 lm / m 2 falls on a flat surface, the outer normal to the direction which forms a beam angle α = 120°. What is the illumination E of the surface?

Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)