Question

Answer needed.

Fast.

Thank you.

Answer 1

2nd option is correct
sinr/sin90=r.i. of air/r.i. of water
sinr=1/4/3
sinr=3/4

sini/sinr=r.i. of water/r.i. of glass
sini/3/4=4/3/r.i.of glass
4sini/3=4/3r.i.of glass
So,
sini=1/r.i. of glass
r.i. of glass=1/sini