Answer:
Option B
Explanation:
Appluing Snell's law at M and N,
sin600=nsinr ............(i)
sinθ=πsin(60−r) ............(ii)
Differentiating we get
cosθdθdn=−ncos(60−r)drdn+sin(60−r)

Differentiating Eq.(i),
ncosrdrdn+sinr=0
or drdn=−sinrncosr=−tanrn
⇒ cosθdθdn=−ncos(600−r)[−tanrn]+sin(600−r)
dθdn=1cosθ[cos(600−r)tanr+sin(600−r)]
From Eq.(i) , r =30° for n=√3
dθdn=1cos60(cos30×tan30+sin30)
=2(12+12)=2