Balance of Beams is Irrelevant

Since both beams of light originate from the same light source, both beams of light see any lamp fluctuations. Recall, the two beams are identical, except for the effect caused by the chirally active sample. If the lamp fluctuates, both beams fluctuate.

• The absolute intensity of the light has no effect on the answer in any single beam or dual beam CD instrument.

• The dual beam CD makes use of no relationship between the beams except the relative phase of polarization, which is set absolutely by the polarizing beamsplitter and which never changes.

• A change in light intensity or detector gain will effect each component in the same proportionate amount, leaving the relationship unchanged.