A spherical surface of radius of curvature R, separates air from glass (refractive index =1.5 ). The centre of curvature is in the glass medium. A…

A spherical surface of radius of curvature R , separates air from glass (refractive index $\displaystyle =1.5$ ). The centre of curvature is in the glass medium. A point object ' O ' placed in air on the optic axis of the surface, so that its real image is formed at ' I ' inside glass. The line OI intersects the spherical surface at P and $\displaystyle \mathrm{PO}=\mathrm{PI}$. The distance PO equals to