Give three examples from your environment of: Points                 (ii)  Portion of a line Plane surfaces    (iv) portion of a plane Curved surfaces

Given three examples of line segments from your environment.

Image formation by refraction from plane and curved surface

Given three examples each of : intersecting lines parallel lines from your environment.

Distance of a point from plane parallel to a line

The maximum number of points of intersection of three lines in a plane is

The minimum number of points of intersection of three lines in a plane is

Given an example of a horizontal plane and a vertical plane from your environment.

A plano-convex lens, when silvered at its plane surface is equivalent to a concave mirror of focal length 28 cm . When its curved surface is silvered and the plane surface not silvered, it is equivalent to a concave mirror of focal length 10 cm then the refractive index of the mateiral of the lens is:

Curve a plane figure formed by joining a number of points without lifting a pencil from the paper and without retracing any portion of the drawing other than single points is called a curve.