MCQ
A beam with wavelength $\lambda$ falls on a stack of partially reflecting planes with separation $d$. The angle $\theta$ that the beam should make with the planes so that the beams reflected from successive planes may interfere constructively is (where $n=1,2, \ldots .$. )
- A$\sin ^{-1}\left(\frac{n \lambda}{d}\right)$
- ✓$\tan ^{-1}\left(\frac{n \lambda}{d}\right)$
- C$\sin ^{-1}\left(\frac{n \lambda}{2 d}\right)$
- D$\cos ^{-1}\left(\frac{n \lambda}{2 d}\right)$
