Two glass lenses of same focal length, one being convex and the other concave, are kept in contact, the combination will act as :

Two convex lenses have focal lengths of 50 cm and 25 cm, respectively. If these two lenses are placed in contact, then the net power of this combination will be equal to

Which one among the following is the correct focal length of a combination of lenses of power 2.5 D and -2.0 D ?

If the lens power of glass is +2 dioptre, its focal length will be-

In a convex lens, if the object is placed at 2F (twice of the focal length), the image formed will be -

A convex lens has a focal length of 15 cm. At what distance should an object be placed in front of the lens to get a real image of the same size of the object?