Two monochromatic light waves of amplitude 3A and 2A interfering at a point have a phase difference of `60^(@)`. The intensity at that point will be proportional to:

Options

A. `3A^(2)`
B. `5A^(2)`
C. `7A^(2)`
D. `9A^(2)`

Answer

C

Explanation

Here, `A_(1)=A,A_(2)=2A, phi=60^(@)`
Amplitiude of the resultant wave, `A_(R)=sqrt(A_(1)^(2)+A_(2)^(2)+2A_(1)A_(2)cosphi)`
`=sqrt(A^(2)+(2A)^(2)+2xxAxx2Axxcos60^(@))=sqrt(7A^(2))`
Intensity `prop (Amplitude)^(2)`
`:.` Intensity `propA_(R)^(2)=7A^(2)`