Bottom of a glass beaker is made of a thin equi-convex lens having bottom side silver polished as shown in the figure. Water is filled in the beaker upto a height 4m. The image of poin to bject,floating at middle point of beaker at the surface of water coincides with it. Find out ther adius of curvature of the lens.Given that refractive index of glass is 3/2 and that of water is 4/3.

Explanation

Focal length of the silvered lens `=-4/2=-2m`
`(f_(l))omega=4(f_(l))a=4R`
`-1/F=2/((f_(l)omega))-1/(f_(m))`
`2/(4R)-1/(-R/2)=5/(2R)`
`impliesR=-(5F)/2=5m`