1). According to its package, a 100 watt light bulb emits 1140 lumens. For simplicity, assume the bulb provides isotropic illumination and ALL its emission is at 555 nm. A video camera is advertised as having "0.2 lux sensitivity", meaning it can record objects which receive at least this illuminance. In a dark room with no other light source, how far away from the light bulb could an object (for example, a white card), be, and still receive just sufficient illumination to be detected by the video camera (assuming normal incidence)?
The maximum distance of the camera from the object is calculated when the minimum illuminance and the power of the source is given.