The focal length of a convex lens is 20 cm. If an object of height 2 cm is placed at 30 cm from the lens, find (i) the position and nature of the image(ii)the height of the image (iii) the magnification produced by the lens.

The focal length of a convex lens is 20 cm. If an object of height 2 c

1.	The focal length of a convex lens is 20 cm. If an object of height 2 cm is placed at 30 cm from the lens, find (i) the position and nature of the image(ii)the height of the image (iii) the magnification produced by the lens.
Answer» Solution :`1/f 1/v - 1/u` ` therefore1/u = 1/f + 1/u = 1/(20 cm) + 1/(- 30 cm) = 1/( 20 cm) - 1/ (30 cm)` ` = ( 3-2)/( 60 cm) = 1/( 60 cm)` v= 60 cm , v is positive. The image will be formed at 60 cm from the lens and on the other side of the lenswith RESPECT to the OBJECT. It is a real image. (ii) ` h_(2)/h_(1) = u/v` ` h_(2)/(2 cm) = (60 cm)/(-30 cm) = -2 ` `h_(20 = -2 XX 2 cm = - 4 cm` `h_(2) ` is negative. This shows that the image is inverted . The height of the image = - 4 cm (III) ` M = h_(2)/h_(1) = ( - 4 cm)/(2 cm) = -2 ` M is negative, indicating that teh image is inverted. The magnification produced by the lens = -2