The radius of curvature for a convex lens is $40 \ cm$ for each surface. Its refractive index is $1.5$. The focal length will be ...... $cm$.

When a biconvex lens of glass having refractive index $1.47$ is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have a refractive index

$A$ lens with a focal length of $50 \ cm$ forms an image of a distant object that subtends an angle of $1 \text{ milliradian}$ at the lens. What is the size of the image in $mm$?

An equiconvex lens has a power of $2 \ D$. If it is made of glass of refractive index $1.25,$ then the radius of curvature of each of its surfaces will be $.... \ cm$.

$A$ thin equiconvex lens is made of glass of refractive index $1.5$ and its focal length is $0.2 \ m$. If it acts as a concave lens of $0.5 \ m$ focal length when dipped in a liquid,the refractive index of the liquid is:

$A$ lens behaves as a converging lens in air but a diverging lens in water,then the refractive index $(\mu)$ of its material is