Young's Double Slit Experiment: Practice Problem & Solution

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Young's Double Slit Experiment. Understanding the underlying formula is key to arriving at the correct answer below:

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 $\frac{2\lambda D}{a} = \frac{10\lambda D}{d} \Rightarrow \frac{2}{a} = \frac{10}{d} \Rightarrow a = \frac{d}{5} = \frac{1}{5} = 0.2 mm$.