The refractive index of a material of a plano-concave lens is $5/3$, and the radius of curvature is $0.3 \,m$. The focal length of the lens in air is (in $\,m$)

You are given two lenses,a converging lens with focal length $+10\, cm$ and a diverging lens with focal length $-20\, cm$. Which of the following would produce a virtual image that is larger than the object?

$A$ thin plano-convex lens of focal length $73.5 \ cm$ has a circular aperture of diameter $8.4 \ cm$. If the refractive index of the material of the lens is $\frac{5}{3}$, then the thickness of the lens is nearly

An object is placed at a distance of $1.50 \, m$ from a screen. $A$ convex lens is placed between them to form a real image four times larger than the object on the screen. The position of the lens is at a distance of ..... (in $, m$)

$A$ convex lens produces a real image $m$ times the size of the object. What will be the distance of the object from the lens?

An object is located in a fixed position in front of a screen. $A$ sharp image is obtained on the screen for two positions of a thin lens separated by $10\, cm$. The size of the images in the two situations are in the ratio $3 : 2$. What is the distance between the screen and the object in $cm$?