IGNAL-to-noise (S/N) ratio theory has proven to be useful in understanding, designing, and optimizing spectrophotometric measurement systems. Although a narrower spectral bandwidth does improve the resolution of closely spaced peaks, it also decreases the Signalto-noise ratio. The narrowest slit width should be used that will yield an acceptable Signalto-noise ratio. In this research, the wavelengths of peak absorbance of the holmium glass filter were determined to attain the optimum Signal-to-noise ratio accompanied with spectral bandwidths of 0.1 nm, 0.2 nm, 0.5 nm, 0.8 nm, 1 nm, 2 nm, 3 nm and 5 nm. The influence of spectral bandwidth on the Signal-to-noise ratio was by far the most important parameter affecting the location of the measured wavelengths of absorbance or transmittance of the sample.

Illumination using artificial light sources is common in these days. Many manufactures are paying for the design of lamps depending on high efficacy and low UV hazards. This research is focusing on the most useable lamps in the Egyptian markets; high pressure mercury (HPM), metal Halide (MH), and high pressure sodium (HPS). A set up for relative spectral power distribution based on single monochromator and UVA silicon detector for absolute irradiance measurements are used. The absolute irradiance in (W/m 2) in UVA region of the lamps and their accompanied standard uncertainty are evaluated.

:Working standards for compact lamps is very important to some inspection organizations in Egypt. We prepare the working standard lamp of high power compact lamp .These lamps provide the realization of luminous flux scale in the photometry laboratory in national institute for standard (NIS). We choose three types of lamps in our study. The lamp types are compact florescent lamp at nominal watt (WL1)

Abstract.Outdoor lighting sources such as High Intensity Discharge lamps (HID) are common in these days. This research is focusing on the relation between the spectral power distribution and luminous efficiency function V (λ), which describes the average spectral sensitivity of human visual perception of brightness. The most useable HID lamps inside Egyptian markets are high pressure mercury (HPM), high pressure sodium (HPS) and metal halide (MH). A set up based on single monochromator and integrating sphere for relative spectral power distribution and absolute luminous flux measurements are used, respectively. The accompanied standard uncertainties with the measurements are evaluated.

Illumination using artificial light sources is common in these days. Many manufactures are paying for the design of lamps depending on high efficacy and low UV hazards. This research is focusing on the most useable lamps in the Egyptian markets; high pressure mercury (HPM), metal Halide (MH), and high pressure sodium (HPS). A set up for relative spectral power distribution based on single monochromator and UVA silicon detector for absolute irradiance measurements are used. The absolute irradiance in (W/m 2 ) in UVA region of the lamps and their accompanied standard uncertainty are evaluated.