In a double slit experiment, if the distance between the slits be reduced to half, then the new fringe width will be

doubled

The correct answer is Option (2) → doubled

Fringe width in double slit experiment: $\beta = \frac{\lambda L}{d}$

If slit separation is halved: $d_\text{new} = \frac{d}{2}$

New fringe width: $\beta_\text{new} = \frac{\lambda L}{d_\text{new}} = \frac{\lambda L}{d/2} = 2 \cdot \frac{\lambda L}{d} = 2 \beta$

Answer: The fringe width becomes twice the original width, $\beta_\text{new} = 2 \beta$