Myopia is the defect of an eye which cannot see the distant (object at infinity) clearly. An eye suffering from this defect forms the image of distant object before retina.
Hypermetropia: In this defect, a person can see the distant objects clearly but not the objects nearer to the eye.
Accommodation is the phenomenon of adjusting the focal length of eye lens in order to focus the image of the object at the retina.
Visual angle: When an object is viewed, the angle subtended by the object at the eye is known as visual angle.
Simple microscope is an optical instrument used to view near objects. It is simply a magnifying glass of converging lens of short focal length.
Angular magnification is defined as the ratio of the angle subtended at the eye by the final image to the angle subtended at the eye by the object when placed at the same distances as the image.
Telescope is an optical instrument which is used to see the distant objects.
Camera: A photographic camera consists of a converging lens system at one end of a light proof box and light sensitive film at the other end. A real inverted image of the object is formed on the film.
fig: Compound Microscope