$A$ double convex lens is made of glass of refractive index $1.5$. If its focal length is $30 \ cm$,then the radius of curvature of each of its curved surfaces is:

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

The power of an equi-concave lens is $-4.5 \ D$ and it is made of a material with a refractive index of $1.6$. The radius of curvature of the lens is: (in $cm$)

The focal length of a lens is $10 \ cm$. What is the power of the lens in dioptre (in $D$)?

$A$ thin converging lens of focal length $f=25 \,cm$ forms the image of an object on a screen placed at a distance of $75 \,cm$ from the lens. The screen is moved closer to the lens by a distance of $25 \,cm$. The distance through which the object has to be shifted,so that its image on the screen is sharp again,is (in $\,cm$)

Assertion: Goggles have zero power.
Reason: Radius of curvature of both sides of the lens is same.