$A$ convex lens is made of $3$ layers of glass of $3$ different materials as shown in the figure. $A$ point object is placed on its axis. The number of images of the object formed is:

$A$ biconvex lens of radius of curvature $R$ is made up of a variable refractive index $\mu = 2[1 + \frac{|y|}{d}]$. Assume $2d << R$. $A$ point object is placed at a distance $R$ on the principal axis as shown in the figure. If the spread of the image lies over a span of $n$ meters,find the value of $n$.

The distance between an object and a divergent lens is $m$ times the focal length of the lens. The linear magnification produced by the lens is

When will the convergent nature of a convex lens be less as compared to its nature in air?

The focal length of a thin converging lens in air is $20 \ cm$. When the lens is immersed in a liquid,it behaves like a concave lens of power $1 \ D$. If the refractive index of the material of the lens is $1.5$,the refractive index of the liquid is

$A$ thin lens with focal length $f$ is to be used as a magnifying glass. Which of the following statements regarding the situation is true?