Q 12-10-152JEE MainJEE Main 2017 (9 Apr)Easy
A single slit of width $0.1$ mm is illuminated by a parallel beam of light of wavelength $6000$ Å and diffraction bands are observed on a screen $0.5$ m from the slit. The distance of the third dark band from the central bright band is:
Answer: (A) $9$ mm
Dark bands are at $y_n = \dfrac{n\lambda D}{a}$:
$$y_3 = \frac{3\times6\times10^{-7}\times0.5}{1\times10^{-4}} = 9\times10^{-3}\ \text{m} = 9\ \text{mm}$$
Solution by Sreeraj P, M.Sc Physics