In Young's doubIe sIit experiment using monochromatic Iight of waveIength `lambda` the intensity of Iight at point on the screen where path difference is `lambda` is k units What the intensity of Iight at a point where the path difference is `(lambda)/(3)` ?

Explanation

Resultant intensity at a point in Young's double slit experiment is
` I=I_(1)+I_(2)+2sqrt(I_(1)I_(2))cos phi`
When path difference = `lambda` phase difference ,
`phi=(2pi)/(lambda).lambda=2pi`
`:.I'=I+I+2sqrt(I.I)=4I`
`:. k=4I`
When path difference `=(lambda)/(3)` phase difference,
`phi=(2pi)/(lambda).(lambda)/(3)=(2pi)/(3)`
`:. I''=I+I+2sqrt(I.I).cos "(2pi)/(3)=I`
`:. I'' =I=(k)/(4)`