The magnification power of a convex lens of focal length 10cm, when the image is formed at the near point is

The magnifying power of a convex lens of focal length 10 cm when the image is formed at the near point is:

The power of a convex lens of focal length 50 cm is …………….

The power of a convex lens of focal length 25 cm is …………… .

The power of convex lens with focal length 40 cm is …………

A convex lens is of focal length 10 cm. What is its power?

An object is placed 30cm away from a convex lens of focal length 10cm and a sharp image is formed on a screen. Now, a convex lens is placed In contact with the convex lens. The screen now has to be moved by 45cm to get a sharp image again. The magnitude of focal length of the convex lends in (in cm)