Question

A square wire of side 2.0 cm is placed 20 cm in front of a concave mirror of focal length 10 cm with its centre on the axis of the mirror and its plane normal to the axis. The area enclosed by the image of wire is

(a) 7.5 cm²

(b) 6 cm²

(c) 2 cm²

(d) 4 cm²

Answer 1

Answer is : (d) 4 cm²

Given, square wire of side = 2 cm,

u = - 20 cm, f = - 10 cm,

Area of second wire = ?

We know that, m = -v/u = -(-20)/20 = -1

∵ Area of image/Area of object = m²