A cast - alloy case supports a tungsten lamp, interference filter, sample holder, photo cell, galvanometer and case cover.
Light from the source tungsten lamp passes through the interference filter and samples to the photo cell, then the transmitted intensity is displayed by the galvanometer.
The tungsten-halogen (usually as quartz - iodine) lamp is constructed with a compact tungsten filament. It's advantage is higher energy in the 300-400 nm range.
The interference filter consists of an evaporated coating of layers of transparent dielectrics of alternating high and low refractive index.
The band of wavelengths transmitted varies across the filter so that wavelength can be scanned from 400-700 nm by moving the filter sideways using a control knob at the front. This allows the absorption spectrum of the sample to be roughly judged, or quantitative measurements of the absorption at a particular wavelength to be made.
TN
