Question

Which of the following is not true for the method of measurement of surface finish by micro interferometer?

(a) Optical flat is used

(b) Monochromatic source of light is used

(c) Depth of defect can’t be measured

(d) Interference lines plays an important role in identification of the defect

I had been asked this question in a job interview.

This interesting question is from Methods of Measuring Surface Finish in section Measurement of Surface Finish of Engineering Metrology

Answer 1

Correct choice is (c) Depth of defect can’t be measured

The best explanation: In the method of inspection of surface by using micro interferometer, an optical flat is used which is placed on the surface to be examined and illuminated by using monochromatic light. Interference bands are studied by using a microscope. Defects or scratches appear as interference lines extending from the dark bands into the bright bands.