Reciprocal of the focal length in metres is known as the ....... of the lens.

The focal length of a lens is given as ........ .

The object u is 2f, a convex len uses as in a ........ .

The ...... image cannot be formed on a screen.

The lens in your eyes are ....... .

The magnification of a concave lens is always......... .

The power of a lens of focal length + 10 cm is ....... .

Both real and virtual images can be formed by a ........ lens.

The object distance is at infinity, a convex lens used as in a ....... .

A ray passing through the ....... of the lens emerges in the same direction.

The virtual image formed by a ....... lens is larger than the object.

When an object is at the centre of curvature of a convex lens,the magnification is ...... .

The distance between the centre of the lens and the focus is the ......... of the lens.

The line ....... the centre of curvatures is the principal axis

A point in the middle of ........ lens on the principal axis is the optical centre of a lens.

A concave is ........ in the middle than at the edges.

The power of lens is ......... proportional to the focal length of the lens.

The power of the lens is ........ .

The principal focus of a concave is ........ .