Illumination of the screen by sunlight falling normally to the screen, E0 = 103 lux; A lens with an optical power of D = 5 diopters is placed in front of the screen at a distance of l = 60 cm. Find the average illumination of the screen in the shadow of the lens and in the light ring around the shadow (Fig.). Neglect the absorption of light in the lens.

Detailed solution. Format gif