GRE question $1$: Light from a laser falls on a pair of very narrow slits

separated by $0\mathrm{.}5$ micrometer, and bright fringes separated by $1\mathrm{.}0$ millime$-$

ter are observed on a distant screen. If the frequency of the laser light is

doubled, what will be the separation of the bright fringes?

$($a$)0\mathrm{.}25$ mm

$($b$)0\mathrm{.}5$ mm

$($c$)1\mathrm{.}0$ mm

$($d$)2\mathrm{.}0$ mm

$($e$)2\mathrm{.}5$ mm