$4)$ Determine what the angle, $,$ should be for the first dark fringe $($m$=0)$ for light with wavelength

of $=10$ units when the slit separation $($d$)$ is $20$ units.

$5)$ If the screen distance $($L$)$ is $100$ units determine the fringe location $()$ for the situation in

question $4($use the $$ you found and a little trig to get there$)$