Question

The transmittance of interference filters varies between ________ % with a spectral bandwidth of 10 to 15 nm.

(a) 15 to 20 %

(b) 20 to 60 %

(c) 10 to 20 %

(d) 15 to 60 %

This question was posed to me in examination.

My query is from Methods of Monitoring Foetal Heart Rate in section Foetal Monitoring Instruments of Biomedical Instrumentation

Answer 1

The correct answer is (d) 15 to 60 %

Easiest explanation: Interference filters allow a much narrower band of wavelengths to pass and are similar to monochromators in selectivity. They are simpler and less expensive. However, as the selectivity increases, the transmittance decreases. The transmittance of these filters varies between 15 to 60 percent with a spectral bandwidth of 10 to 15 nm.