When the light ray illustrated in the figure below passes through the glass block of index of refraction $n=1\mathrm{.}50,$ it is shifted laterally by the distance $d.($Let $L=2\mathrm{.}31.$ cm and $=31\mathrm{.}0.)$

$($a$)$ Find the value of $d.$

cm

$($b$)$ Find the time interval required for the light to pass through the glass block.

ps