Simple Microscope or Magnifying glass
This instrument is used for small magnification. It contains a convex lens of small focal length placed in a frame having a handle [Figure]. It is actually a convex lens of small focal length, which is used for seeing the magnified images of small objects. Normally, it is used to see fine paintings, small points, small types, very small instruments etc. It is also used by the jewelers to see the magnified view of the fine parts of jewelry.
Working principle: We know, if an object is placed at a distance smaller than the focal length of a convex lens, then an erect, virtual and magnified image is formed on the same side of the object and nearer the object to the lens, larger is the magnification of the object or the image is formed at greater distance from the lens. The magnifying power or angular magnification of a microscope may be defined as the ratio of the angle subtended at the eye by the image formed at the distance of the distinct vision to the angle subtended by the object when placed at the distance of the distinct vision. Placing an eye on the other side of the lens, this magnified image will be seen instead of the object. If the distance of the lens from the object is so adjusted that the image is formed at the least distance of distinct vision, the eye will see the magnified image clearly without any strain on the eye. This is the basic principle for a simple microscope.