Question

colours having no existence in optical surface

Answer 1

Hey mate... Optical flat is your answer..

Answer 2

Answer: The surface in which the colours having no existence in optical surface is the optical flat.

Explanation:

The optical flat is usually used for testing when placed on a flat surface. All we need for testing is the illumination with white light.

That illuminating of white light can be achieved by interference fringes of rainbow coloured bands are formed. The optical flat must be placed on clean and reflect surface.