Question 21:
moderateIn a double slit experiment, the two slits are 1 mm apart and the screen is placed 1 m away. A monochromatic light of wavelength 500 nm is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern?
(2015)
Width of central maximum of single slit is $W_s = \frac{2\lambda D}{a}$. Fringe width of double slit is $\beta = \frac{\lambda D}{d}$. Given $W_s = 10\beta$, so $\frac{2\lambda D}{a} = \frac{10\lambda D}{d} \Rightarrow \frac{2}{a} = \frac{10}{d} \Rightarrow a = \frac{d}{5} = \frac{1}{5} = 0.2 mm$.