is placed perpendicular to the principal axis of a convex lens of focal length cm. The distance of the object from the lens is cm. Find the nature, position and size of the image. Also find its magnification.
Solution Height of the object h = + . cm; Focal length f = + cm; object-distance u = – cm; Image-distance v = ? Height of the image h ′ = ? Since or, ( ) v = = − or, v = + cm The positive sign of v shows that the image is formed at a distance of cm on the other side of the optical centre.
The image is real and inverted. Magnification m = ' or, h ′ = h ( v / u ) Height of the image, h ′ = ( . ) (+ /– ) = – . cm Magnification m = v/u or, 30cm 15cm m = − The negative signs of m and h ′ show that the image is inverted and real.
It is formed below the principal axis. Thus, a real, inverted image, cm tall, is formed at a distance of cm on the other side of the lens. The image is two times enlarged.