Same size of image is formed by a convex lens of focal length 20 cm . The distance betweenthe object and image is(a) 0 cm (b) 20 cm(c) 40 cm (d) 80 cm1

The question is asking for the distance between the object and the image formed by a convex lens with a focal length of 20 cm, given that the size of the image is the same as the object.

This means that the image formed is a real image and is inverted.

The lens formula is given by 1/f = 1/v - 1/u, where f is the focal length, v is the image distance, and u is the object distance.

Since the image is the same size as the object, the magnification m = -v/u = -1.

This implies that v = -u.

Substituting v = -u into the lens formula gives 1/f = -2/u.

Solving for u gives u = -2f.

Given that the focal length f is 20 cm, the object distance u is -2*20 cm = -40 cm.

However, since we are looking for the distance between the object and the image, we take the absolute value, which is 40 cm.

So, the correct answer is (c) 40 cm.