$A$ convex lens forms a real image of a point object placed on its principal axis. If the upper half of the lens is painted black,the image will

The optical axis of a thin equiconvex lens is the $x$-axis. The coordinates of the object and its image are $(-40 \, cm, 1 \, cm)$ and $(50 \, cm, -2 \, cm)$ respectively. Find the position of the lens.

$A$ convex lens of focal length $12 \ cm$ is made of glass of refractive index $\mu_g = \frac{3}{2}$. What will be its focal length when immersed in a liquid of refractive index $\mu_l = \frac{5}{4}$? (in $cm$)

$A$ convex lens of focal length $1/3 \ m$ forms a real,inverted image twice the size of the object. The distance of the object from the lens is: (in $m$)

An object is placed in front of a convex lens,and an image of height $8 \, cm$ is formed. When the lens is moved to a new position,the image height becomes $2 \, cm$. Find the height of the object in $cm$.

$A$ thin lens made of glass (refractive index $= 1.5$) of focal length $f = 16 \; cm$ is immersed in a liquid of refractive index $1.42$. If its focal length in liquid is $f_{l}$,then the ratio $f_{l} / f$ is closest to the integer: