An observer can see through a pin-hole the top end of a thin rod of height h, placed as shown in the figure. The beaker height is 3h and its radius h. When the beaker is filled with a liquid up to a height 2h, he can see the lower end of the rod. Then the refractive index of the liquid is

Answer

B

Explanation

`PQ=QR=2h`
`:. anglei=45^@ `
` :. ST=RT=h=KM=MN `
So, `KS=sqrt(h^2+(2h)^2)=hsqrt5 `
` :. Sinr=h/(hsqrt5)=1/sqrt5 `
`:. mu=sini/sinr=sin45^@/(1//sqrt5)=sqrt(5/2)`
`:.` The correct answer is.