Question

A single beam spectrophotomer measures a sample's absorbance 0.5 What would happen to the measured absorbance at the detector of the light source was moved AFTER the sample cuvet in the spectrophotomer? *A*0.5 005 A 1 -0.5

Answer 1

Moving the light source in a spectrophotometer after the sample cuvet would prevent accurate determination of initial light intensity (Io) and render the absorbance measurement meaningless since the light must pass through the sample to compare Io and I.

Step-by-step explanation:

If the light source in a spectrophotometer was moved to a position after the sample cuvet, the detected absorbance would be significantly affected. Absorbance is measured by comparing the intensity of light before it passes through the sample (Io) with the intensity after it passes through the sample (I). When the light source is positioned correctly before the sample cuvet, the spectrophotometer takes the intensity of the incoming light (Io), passes it through the sample, and measures the remaining intensity (I) to calculate the absorbance, which is a logarithmic ratio of Io to I.

If the light source were moved after the sample, this Io value could not be accurately determined, as the light would not pass through the sample before measurement. Thus, it would not provide a meaningful measure of absorbance. In proper spectrophotometry practice, the light must travel a known path length through the sample for accurate absorbance measurements and to maintain the unit's calibration which often assumes a 1 cm path length for calculations.