Types and uses of lenses in our life & special concepts related to the lenses
The lens is the transparent medium that refracts the light and it is limited with two spherical surfaces, The lens is usually made of the glass or the plastic, The lens is the transparent optical device that affects the focus of a light beam through the refraction.
Importance of lenses
A simple lens consists of a single piece of material while a compound lens consists of several simple lenses (the elements), usually along a common axis.
the lenses are made from transparent materials such as the glass, then ground and polished to the desired shape, The lens can focus the light to form an image, unlike a prism, which refracts the light without focusing.
The devices that similarly refract radiation other than visible light are also called the lenses such as the microwave lenses or the acoustic lenses.
The lenses are used in many things, They are used in the medical eyeglasses either for reading or walking, They are used in the wars, the leaders use the binoculars to follow the battles.
The person who fixes the watches use a magnifier lens to see the minute parts of the watches, The lenses are used in the manufacture of many things as the projector, the cameras, and the magnifying lenses.
The lenses are used in Microscopes which are used for formation magnified images of the tiny bodies that can not be seen with the naked eye and they are used in making of medical glasses to treat the vision defects.
Types of lenses
The convex lens is thick at the center and less thickness at the tips, It collects the light rays falling on it, So, it is called the converging lens .
The concave lens is thin at its center and thicker at the tips, It separates the light rays, So, it is called the diverging lens.
Special concepts related to the lenses
The center of the curvature of the lens face (C) is the center of the sphere, where this face is a part of it, The optical center of the lens is a point inside the lens lies on the principal axis in the mid-distance between its faces.
The radius of curvature of the face of the lens is (r) half the diameter of the sphere, where this face is a part of it, The principal axis is the straight line that joins between the two centers of curvature of the lens passing by the optical center of the lens.
The secondary axis is any line passes by the optical center of the lens except the principal axis, The focal length of the lens (f) is the distance between the focus and the optical center of the lens, (f = ½ r).
The focus of the lens (F) (the principal focus) is the point of collection of the refracted light rays (in the convex lens) or their extensions (in the concave lens), It is produced when a beam of parallel rays falls parallel to the principal axis of a lens.
The focus of the lens is real in the case of the convex lens and it is virtual in the case of the concave lens, Each lens has only one principal axis and more than one (uncountable number) of secondary axes.
The lens has two centers of curvature and it has two foci because it has two circular surfaces.