A ray of light falls on a transparent sphere with centre at C as shwon in figure. The ray emerges from the sphere parallel to line AB. The refractive index of the sphere is

Explanation

Deviation by a sphere is 2(I -r)
Here deviation `delta=60^@=2(i-r) or i-r =30^@`
`therefore r=i-30^@ =60^@-30^@= 30^@`
`therefore mu = (sin i)/ (sin r)= (sin 60^@)/(sin 30^@)=sqrt3`