A lens which is thinner at the edges and thicker at the centre is known as convex lens.
Generally lenses are made up of glass or transparent plastic and the same can be used for transmitting, refracting or for focusing the light.
A convex lens is supposed to be made up of number of prisms with the base of each prism towards the centre of the lens.
When rays parallel to the principal axis pass through a convex lens, they are bent inwards.
The point at which they converge is known as principle focus.
The distance from the principle focus to the centre of the lens is known as focal length.
This type of lens bends the light inwards.
Example: Magnifying glass.
When an object is placed closer to a convex lens than the principle focus, the rays never converge and magnified image is formed on the same side of the object.
Thick, bulging convex lenses have the shortest focal lengths, which are commonly used as powerful magnifying glasses.