Question

Which of the following detector is required in spectrophotometer?

(a) Phototransistor

(b) Photodiode

(c) LDR

(d) Photomultiplier

The question was asked during an interview.

The doubt is from Pneumotachometers topic in section Pulmonary Function Analysers of Biomedical Instrumentation

Answer 1

Right choice is (d) Photomultiplier

To elaborate: The amount of light reaching the detector of a spectrophotometer is generally much smaller than that available for a colorimeter, because of the small spectral bandwidth. Therefore, a more sensitive detector is required. A photomultiplier or vacuum photocell is generally employed.