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

In a double slit experiment, fringe width is given by:

$\beta = \frac{\lambda L}{d}$

where $L$ = distance to screen, $d$ = slit separation, $\lambda$ = wavelength of light.

If the slit separation is reduced to half, $d' = \frac{d}{2}$, then the new fringe width:

$\beta' = \frac{\lambda L}{d'} = \frac{\lambda L}{d/2} = 2 \frac{\lambda L}{d} = 2\beta$

∴ The new fringe width = 2 × original fringe width