A convex lens of focal lenth 30 cm and a concave lens of focal length 60 cm are placed in contact.Find the power of the combination.

A convex lens of foal length 30 cm and a concave lens of focal length 60 cm are placed in contact.If the object is placed 40 cm away from the combination ,, find the position of the image.

Two lenses of focal length 10 cm and -20 cm are placed in contact .What is the total power of the combination?

A concave lens is kept in contact with a convex lens of focal length 20 cm.The combbination works as a convex lens of focal length 50 cm.Find the power of the concave lens.

If a convex lens of focal length 80 cm and a concave lens of focal length 50 cm re combined together ,what will be their resulting power?

The size of the image of an object,which is at infinity, as formed by a convex lens of focal length 30 cm is 2 cm. If a concave lens of focal length 20 cm is placed between the convex lens and the image at a distance of 26 cm from the convex lens, calculate the new size of the image

A concave lens is kept in contact with convex lens of focal length 20 cm.The combination works as convex lens of focal length 50 cm. Find the power of concave lens.