Light Sensors appear to be quite simple. They detect light in the same way as a thermometer detects temperature and a speedometer detects speed. We perceive temperature and speed in a straightforward manner, making them simple concepts. But light is incredibly intricate. Since temperature and speed are intense qualities, they are independent of an object's mass or size. Light can be measured either extensively by dividing by the area, in which case the amount of light collected depends on the size of the collector (for example, a huge solar array collects more light than a little solar phone charger).
The entire luminous flux of a light bulb is measured in lumens. This is the result of the solid angle that the beam fills and the luminance intensity (measured in candelas) (in steradians). When the whole 4 steradians are multiplied by the luminous intensity of 10 candelas, which comes from a bulb that emits light in all directions, the result is a luminous flux of 126 lumens. Similar to inside a flashlight, a mirror on one side of the bulb would reflect half of its output, making the other side appear brighter. The solid angle would only be 2 steradians, but the light's intensity would increase to 20 candelas. Even after multiplying the light's intensity from the mirror's opposite and the new solid angle, 126 lumens of luminous flux would still be produced. This Light Sensors bulb will always emit 126 lumens of luminous flux, regardless of how the light is refracted and focused.
