Question

The power of convex lens is positive or negative?

Answer 1

the power of convex lense is positive.

Answer 2

The power of the convex lens is positive.  

The power of the lens is p=1/f, where f is the focal length.

The power is positive only if the focal length is positive (right side of the lens) and the power is negative if the focal length is negative (left side of the lens).

In the convex lens, the center of the lens is thicker and the corners of the lens are thinner. They converge all the lights and display real and inverted object at the right side of the focal point. So the power of the convex lens is positive.