used as a bandpass filter, these filters transmit light where the refractive index of the material matches that of the light. This wavelength changes with temperature, so when using one of these filters the temperature must be kept roughly constant. Found on http://www.chemistry-dictionary.com/definition/christiansen+filter.php
used as a bandpass filter, these filters transmit light where the refractive index of the material matches that of the light. This wavelength changes with temperature, so when using one of these filters the temperature must be kept roughly constant.