In interference, two individual amplitudes are `A_0` each and the
intensity is `I_0` each. Find resultant amplitude and intensity at a point, where:
(a) phase difference between two waves is `60^@`.
(b) path difference between two waves is `lambda/3`.

Answer

A, B, C, D

Explanation

(a) Substituting `phi=60^(@)` in the equations,
`A=2A_0 (cos)phi/2` …….(i)
and ` I=4I_0 cos^2 (phi/2)` ……..(ii)
We get, `A= (sqrt3)A_0 and I=3I_0`
(b) Given, `Deltax =lambda/3`
`:.phi or Delta phi = ((2pi)/lambda). Deltax`
`=((2pi)/lambda)(lambda/3) = (2pi)/3 or 120^@`
Now, substituting `phi=120^@` in the above two equations we get
`A=A_0 and I=I_0` .