The relationship between light intensity and resistance is inverse. This means that as light intensity increases, resistance decreases. This is due to the photoelectric effect, where photons from light can knock electrons off of atoms, making it easier for electricity to flow and decreasing resistance.
The unit of measurement for light intensity is the candela (cd). This measures luminous intensity, or the amount of visible light emitted per unit solid angle in a particular direction. Other units for light intensity include lux, which measures the amount of light falling on a surface, and foot-candle, which is the imperial unit for lux.
Light intensity can be measured using a device called a photometer, which measures the amount of light in a given area. This can also be done using a light meter, which measures the amount of light in a specific location. Light intensity can also be measured indirectly by measuring the voltage or current in a circuit that is affected by light.
Temperature can affect both light intensity and resistance. As temperature increases, the atoms in a material vibrate more, making it harder for electrons to flow and increasing resistance. This can also affect light intensity, as changes in temperature can cause changes in the material's ability to absorb and emit light. For example, as temperature increases, the amount of light emitted by a heated object also increases.
The type of material can greatly affect the relationship between light intensity and resistance. For example, materials with a higher number of free electrons, such as metals, will have a stronger photoelectric effect and therefore a greater decrease in resistance with increasing light intensity. On the other hand, materials with a lower number of free electrons, such as ceramics, will have a weaker photoelectric effect and a smaller change in resistance with changing light intensity.