23. maximum intensity of interterence colours occurs when the value or retardaion is equal to (a) (b) (2n+ 1) (c) an (d) zero

yes they are correct but we don't really use them. Actually we use A as the basic or general formula for max intensity even in case of optical physics.

This is purely based on optics(physics concept) . As you have already read these things in class 12 th optics chapter, I will keep it simple. When two waves are travelling in a m...