Question

If any surface has a scratch on it and surface is tested by surface contour test then, what is the depth of scratch? (D= distance between fringes, d= distance due to scratch)

(a) (d/D)*(λ)

(b) (d/D)*(λ/2)

(c) (d/D)*(λ/4)

(d) (d/D)*(3λ/2)

I have been asked this question in my homework.

Enquiry is from Surface Contour Test topic in division Measurement by Light-Wave Interference of Engineering Metrology

Answer 1

Right option is (b) (d/D)*(λ/2)

To explain I would say: Surface contour method is used for many purposes. It is possible to determine depth of the scratch, high and low spots or hills and valleys, and surface worn at the edges. These all can be determined by this method.