Reflection, Superposition & Interference question from NEET 2008 (AIPMT)

Answer: (b)

1. $I_{max} = \left(\sqrt{I_1} + \sqrt{I_2}\right)^2$, $I_{min} = \left(\sqrt{I_1} - \sqrt{I_2}\right)^2$.
2. Adding, the cross terms $\pm 2\sqrt{I_1 I_2}$ cancel: $I_{max} + I_{min} = 2(I_1 + I_2)$.
3. So the answer is (b) $2(I_1 + I_2)$.