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