What is a detectors spectral sensitivity curve?

The relationship between the sensitivity of a photoelectric surface and the wavelength of incident light is referred to as the "spectral sensitivity characteristic." It is mainly determined by the material of the photoelectric surface. This slide shows the spectral sensitivity characteristic of a multi-alkali photoelectric surface that has sensitivity in the ultraviolet and visible region. There are other “types” of PMT’s that shift the detectors peak sensitivity into different wavelength regions. Picture the curve presented here “sliding” the sensitivity curve to higher or lower wavelengths. The curve presented here is a “red sensitive” R-928 PMT.