Optical Instruments, Dispersion and ScatteringIn the previous chapter, we have seen that a convex lens can produce real or virtual image of objects. An optical instrument is a device which helps us to see or record such images. Human eye is an optical instrument provided by nature. It is a remarkably effective organ, but its range can be extended in many ways by optical instruments such as eye glasses, simple magnifying lenses, microscopes and telescopes. The structure and working of human eye is very similar to that of a photographic camera.