Two slits are made 0.8 mm apart and the screen is placed 1.5 m away. What should be the width of each slit to obtain 8 maxima of the double slit pattern within the central maximum of the single slit pattern?

0.2 mm

The correct answer is Option (1) → 0.2 mm

Number of double-slit maxima inside the single-slit central maximum:

$N=\frac{2d}{a}$

Given $N=8 \;\;\Rightarrow\;\; a=\frac{2d}{8}=\frac{d}{4}$

Since $d=0.8 \;\text{mm}$

$a=\frac{0.8}{4}=0.20 \;\text{mm}=2.0\times10^{-4}\;\text{m}$

Final Answer: $a=0.20 \;\text{mm}=2.0\times10^{-4}\;\text{m}$