In a two-slit interference pattern, the maximum intensity is `l_0`.
(a) At a point in the pattern where the phase difference between the waves from the two slits is `60^@`, what is the intensity?
(b) What is the path difference for 480nm light from the two slits at a point where the phase angle is `60^@`?

Explanation

(a)`I=I_(max) "cos"^2 phi/2`
`=I_0 cos^2 30^@ (as phi= 60^@)`
` = 3/4I_0` .
(b) `60^@` phase difference is equivalent to `lambda/6` path difference.