Question

Which of the following is the method to test parallelism in Type-B optical flats?

(a) Hawking interferometer

(b) Enrico interferometer

(c) Fizeau interferometer

(d) Stephan interferometer

This question was posed to me by my college professor while I was bunking the class.

I need to ask this question from Optical Flats topic in section Measurement by Light-Wave Interference of Engineering Metrology

Answer 1

Right answer is (c) Fizeau interferometer

The explanation is: Fizeau interferometer is used to test parallelism in optical flats. In this test a light from mercury vapour lamp is focused on eye-piece. Beam splitter is used to reflect the beam which strikes the collimating lens. It collimates the beam and throw it on the surface under test.