Question
Find the intensity at a point on a screen in Young’s double slit experiment where the interfering waves of equal intensity have a path difference of (i) $\lambda/4$, and (ii) $\lambda/3$.

Answer

Path difference 𝜆/4 ⟹ phase difference 𝜋/2
Path difference 𝜆/3 ⟹ phase difference (2𝜋/3)
$I=4I_0\cos^2\Big(\frac{\theta}{2}\Big)$
  1. $I_1=4I_0\times\frac{1}{2}=2I_0$
  2. $I_2=4I_0\times\frac{1}{4}=I_0$

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