A point object is placed at the centre of a glass sphere of radius 6 cm and refractive index 1.5. The distance of the virtual image from the surface of the sphere is

Using refraction formula  1μ2−1R= 1μ2v−1uin given case, medium (1) is glass and (2) is airso gμa−1R= gμav−1u⇒11.5−1−6=11.5v−1−6⇒1−1.5−6=1v+1.56⇒0.56=1v+14⇒1v=112−14=−212=−16⇒v=6 cm