A thin lens made of a material of refractive index μ2 has medium with refractive index μ1 and –μ3 on either side. The lens is biconvex and the two radii of curvature has equal magnitude R. A beam of light travelling parallel to the principal axis is incident on the lens. Where will the image be formed it the beam is incident from (a) the medium μ1 and (b) from the medium μ3
