Discussion
Photomultiplier can detect a feeble optical signal because of :
Answer: C
A photomultiplier detects feeble light because of the multiplication of secondary electrons.
A photon striking the photocathode releases a photoelectron, which is accelerated to the first dynode and knocks out several secondary electrons. Each of these is accelerated to the next dynode and multiplied again, so after about ten stages one photoelectron becomes a pulse of a million electrons.
The photons themselves are not multiplied, the shape of the photocathode only affects collection, and multiplying the output pulse would add nothing that is not already in the signal.
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