Question

A typical reflection grating may have 1200 grooves/mm, which means the grooves are spaced at about _______ intervals.

(a) 800 nm

(b) 600 nm

(c) 860 nm

(d) 680 nm

This question was addressed to me in a national level competition.

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

Answer 1

The correct choice is (a) 800 nm

Explanation: A typical reflection grating may have 1200 grooves/mm, which means the grooves are spaced at about 800 nm intervals. The grating may have a width of 20 mm or more, giving a total of at least 24,000 grooves.