The illuminance of a screen situated at a distance of 5m from an electric bulb of power
Channel: Doubtnut
Date: 2021-11-02

The illuminance of a screen situated at a distance of 5m from an electric bulb of power 500 watt is 120 `"lumen"//m^(2)`. Assuming normal incidence of light on screen calculate (i) the luminous intensity of the bulb and (ii) the luminous efficiency of the bulb.