Question

1 sec of arc will correspond to how much rise or fall in surface, when surface straightness is tested by autocollimator? (λ is the distance between centres of feet)

(a) 0.000006λ

(b) 0.00006λ

(c) 0.00006λ

(d) 0.0006λ

I got this question in examination.

The doubt is from Test for Straightness by using Spirit Level and Autocollimator in division Straightness, Flatness, Squareness, Parallelism, Circularity and Rotation of Engineering Metrology

Answer 1

Correct answer is (a) 0.000006λ

To elaborate: In this method, reading of tilt of the reflector is taken in seconds from the eyepiece. 1 second of arc is 0.000006 mm/mm. It also depends upon the distance between feel centres in millimeter.