In a double slit experiment, if the distance between the slits be reduced to half, then the new fringe width will be
Answer & explanation
Correct answer: option 2
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