A photometer reads an illuminance of from a test lamp

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Geometrical optics and imaging · Geometrical optics and imaging

What an Instrument Can See, Ch Radiance, etendue and a throughput budget that is spent

Problem

A photometer reads an illuminance of 50 lux50\ \mathrm{lux} from a test lamp. Using the conversion that one lux from a 5800 K5800\ \mathrm{K} black-body spectrum corresponds to about 1.1×104 photons s−1 μm−21.1\times10^4\ \mathrm{photons\,s^{-1}\,\mu m^{-2}} (integrated over 400400-700 nm700\ \mathrm{nm}), and that one lux from a 2856 K2856\ \mathrm{K} tungsten spectrum corresponds to about 1.2×104 photons s−1 μm−21.2\times10^4\ \mathrm{photons\,s^{-1}\,\mu m^{-2}} over the same band: ((a)) Find the photon flux density in photons s−1 μm−2\mathrm{photons\,s^{-1}\,\mu m^{-2}} if the lamp is a 5800 K5800\ \mathrm{K} source. ((b)) Find it if the same illuminance instead came from a 2856 K2856\ \mathrm{K} tungsten source.

Browse the problem library