Question

Which of the following is true for testing flatness with optical flats?

(a) Too large angle of work with flat is desirable

(b) Number of bands appears is an indication of flatness

(c) Bands are viewed as perpendicularly as possible

(d) Quartz flats are very sensitive to temperature changes

I got this question by my school principal while I was bunking the class.

Origin of the question is Flatness Testing topic in section Straightness, Flatness, Squareness, Parallelism, Circularity and Rotation of Engineering Metrology

Answer 1

The correct answer is (c) Bands are viewed as perpendicularly as possible

The explanation is: Due to very great angle between work and flats, bands will be close together and are nearly invisible. Number of bands appear is not an indication of the surface flatness but relates only to the wedge steepness.