Light Sensors: Units, Uses, and How They Work

Light sensors seem pretty simple. They sense the light, just like a thermometer senses the temperature, and a speedometer senses speed. Temperature and speed are easy to comprehend because we sense them in a straight-forward way. But light is very complicated. Temperature and speed are intensive properties, so they don’t depend on the mass or size of an object.  Light can be measured as an extensive property, meaning the total light collected depends on the size of the collector (e.g. a landfill solar array collects more light than a tiny solar phone charger), or intensively by dividing by the area.

But what are light sensors even measuring? Photons? Energy? It’s complicated. The units are important to understand before attempting to understand light sensors.