The visible phase signal is modeled as the ideal count scaled by the coherent fraction, so reduced coherence directly lowers the checked signal. The multiplication is exact only for the declared ideal count and fraction; laboratory estimates carry shot noise, contrast calibration error, background drift, and uncertainty in the coherence estimate.
The visible phase signal is the ideal count times the coherent fraction. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
Three fourths coherence scales the visible count
The ideal visible count is 40. Multiplying by 3/4 gives 30.
Nvisible=40⋅43=30
One half coherence gives a smaller visible count
With coherent fraction 1/2, the same ideal count 40 gives 20 visible counts.