Question

What is the condition to obtain fringes of high intensity?

(a) Distance between scale and index grating is as far as possible

(b) Distance between scale and index grating is minimum

(c) Scale and index grating should be overlapped

(d) Scale and index grating should be at the right angle

I have been asked this question in exam.

This key question is from Scales and Gratings topic in portion Measurement by Light-Wave Interference of Engineering Metrology

Answer 1

Correct option is (b) Distance between scale and index grating is minimum

The best explanation: Fringes of high intensity means good contrast. It is the essential condition for obtaining good electrical signals. It can be obtained only when the distance between the scale and index grating is minimum.