What unit of measurement is used to measure light intensity?
Luminous intensity
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela(cd), an SI base unit.
Fluorescence interference contrast microscopy
The observed fluorescence intensity, formula_1, is the product of the excitation probability per unit time, formula_2, and the probability of measuring an emitted photon per unit time, formula_3. Both probabilities are a function of the fluorophore height above the silicon surface, so the observed intensity will also be a function of the fluorophore height. The simplest arrangement to consider is a fluorophore embedded in silicon dioxide (refractive index formula_4) a distance "d" from an interface with silicon (refractive index formula_5). The fluorophore is excited by light of wavelength formula_6 and emits light of wavelength formula_7. The unit vector formula_8 gives the orientation of the transition dipole of excitation of the fluorophore. formula_2 is proportional to the squared projection of the local electric field, formula_10, which includes the effects of interference, on the direction of the transition dipole. 