Task id16618

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.