Two identical light waves having phase difference `'phi'` propagate in same direction. When they superpose, the intensity of resultant wave is proportional to

Options

A. `cos^(2) phi`
B. `cos^(2) 'phi/2`
C. `cos^(2)'phi/3`
D. `cos^(2)'theta/4`

Answer

B

Explanation

For two cherent sources the resultant intensity is given as.
`I_(R) = I_(1) + I_(2) + 2sqrt(l_(1)I_(2)) cos phi`
`:.` For two identical light waves,
`I_(1) = I_(2) = I`
`rArr I_R = 4I cos ^(2)' (phi)/(c )`
`:. I_(R) = cos^(2) '(phi)/(2)`