Which lens is used in magnifying glass?
(A) Concave lens
(B) Convex lens
(C) Bipolar lens
(D) Cylindrical lens

Hint A transparent material bound by two surfaces, of which one or both surfaces are spherical forms a lens. This means the lens is bound by at least one spherical surface and the other surface would be plane.

Complete step-by-step answer:
A convex lens is thicker at middle as compared to the edges and a concave lens is thicker at the edges than the middle.
Similarly, magnifying glass is thicker at the middle as compared to edges. Convex lenses produce magnified images as the magnifying lenses do. Convex lenses allow to make objects larger likewise the magnifying lenses do.
Now let us match these properties with the given options:
(A) Concave lens: these lenses produce very diminished images ( point size images ) but magnifying lenses produce enlarged images. Thus, this option is not correct.

(B) Convex lenses: these lenses produce magnified images and make objects larger as magnifying lenses do. Thus, this option is correct.

(C) Bipolar lenses: these lenses are used to correct vision of the eyes and contain both lenses convex and concave. Thus this option is not correct.

(D) Cylindrical lenses: it contains one plane lens and one convex or concave lens and is used to correct astigmatism. Thus this option is not correct.

Our required answer is (b) that is convex lenses.

Note A lens may have two spherical surfaces, bulging outwards. Such a lens is called a double convex lens. It is simply called a convex lens. It is thicker in the middle as compared to the edges Convex lens converges light rays.