Answer
$89.1\mu m$
Work Step by Step
We can find the required separation as follows:
$tan\theta=\frac{y}{L}$
$\theta=tan^{-1}(\frac{y}{L})$
$\implies \theta=tan^{-1}(\frac{5.36\times 10^{-2}}{8.75})=0.351$
Now $d=\frac{n\lambda}{sin\theta}$
We plug in the known values to obtain:
$d=\frac{(1)(5.46\times 10^{-7}m)}{sin(0.351)}$
$d=8.91\times 10^{-5}m$
$d=89.1\mu m$
