A ray of light passes through an equilateral glass prism in such a manner that the angle of incidence is equal to the angle of emergence and each of these angles is equal to $(\frac{3}{4})th$ of the angle of prism. The angle of deviation is:

30°

The correct answer is Option (4) → 30°

The angle of deviation is,

$D=i+e-A$

$=i+e-A$   $[i=e=\frac{3}{4}×60=45]$

$=2×45-60$

$=30°$