Biology 2290F/G Study Guide - Final Guide: Hemocytometer, Diffraction Grating, Radiant Flux
10 Nov 2012
School
Department
Course
Professor
Document Summary
Radiant energy is focused onto a diffraction grating which splits the light into its component wavelengths. Different wavelengths can be selected by changing the position of the grating, allowing only a narrow range of wavelength to pass through the slit and reach the sample. This current is measured by a galvanometer (amp meter) It compares measured transmittance to that of a reference blank to determine absorbance. Any light not absorbed (transmitted) by the sample reaches a phototube that converts it to electrical current. Output information is both transmittance and absorbance, but the machine only measures transmittance. Absorbance is the amount of light absorbed by a sample. Transmittance is the fraction of light that passes through the sample. Lambert"s law: for a thin layer of ample, the same proportion of light is absorbed regardless of the radiant power of the incident light.
