MEASUREMENT OF TRUE TRANSMITTANCE OF SAMPLES MOUNTED ON AN APERTURE PLATE

Double beam commercial spectrophotometers usually accept samples large r than a specific size. In case samples are undersized, these samples for their transmittance measurement are mounted on an aperture plate. In order to maintain the precision of the measurement and also not to disturb the optical balance between two beams, a similar aperture plat e is placed in the reference beam of the spectrophotometer. In spite o f all the precautions taken the measurement often leads to an erroneou s result. A simple methodology to derive values of true/actual transmi ttance value when the samples are mounted on an aperture plate is disc ussed here.