Consider interference between waves form two sources of intensities `I&4I`.Find intensities at point where the phase difference is `pi`

Options

A. `I`
B. `5I`
C. `4I`
D. `3I`

Explanation

`I=R^(2)=a_(1)^(2)+a_(2)^(2)_2a_(1)a_(2)cosdelta`
`=I+4I+4Icospi`
`I=5I-4I=I`