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INTRODUCTION

A lens is conventionally defined as a piece of glass which is used to focus or change the direction of a beam of light passing through it. They are mainly made of glass or plastic. Lens are used in making spectacles, cameras, cinema projectors, microscopes and telescopes.

 

Types of thin lenses.

A lens which is thicker at its centre than at its edges converges light and is called convex or converging lens. A lens which is thicker at its edges than at its centre diverges light and is known as concave or diverging lens.

       

                                                   Human eye