APPLICATIONS OF LENS
SIMPLE MICROSCOPE: Microscope or magnifying glass is a convex lens which is used to produce a magnified image of small objects. It is also used for reading small prints and for studying biological specimens.
In applying the lens, it’s placed nearer to the object so that the object distance is within the focal length. As such, the image formed is magnified, the lens is moved until the image is distinctly seen at 25cm or 0.25m from a normal human eye. The magnifying power of a simple microscope depends on its focal length such that the direction of the relationship is indirect.
COMPOUND MICROSCOPE
To produce higher magnification than that obtained from a simple microscope, a combination of two convex lenses is used in an arrangement called the compound microscope.
The compound microscope consists of two convex lenses of short focal length. The lens nearer the object is known as the objective lens and the lens through which the final image is seen is known as the eyepiece. The eyepiece has a larger focal length than the objective lens.
THE ASTRONOMICAL TELESCOPE
The telescope is used in viewing distant objects, such as the stars and planets. The simplest telescope is the astronomical telescope.
The astronomical telescope uses two convex lenses (objective lens and eyepiece respectively). The objective lens has a long focal length whereas the eyepiece has a short focal length.
THE GALILEAN TELESCOPE
This type of telescope uses a convex lens of long focal length as the objective lens and the concave lens of short focal length as the eyepiece. The two lenses are mounted so that they leave a common axis with the distance between them equals to the difference between their focal length.
The magnifying power of the telescope is given by:
M = focal length of objective lens (F0)/ focal length of eyepiece (Fe)
PRISM BINOCULARS: they are essentially pair of astronomical telescopes each of which is fitted with two right-angled isosceles prisms. They have the advantage of bringing the rays from two telescopes inwards to match the distance apart of the two eyes.
THE PROJECTOR: the simple lens camera consists of a light-proof box with a convex lens in front and a light-sensitive film at the back. The function of the lens is to focus images of the object to be photographed unto the light-sensitive film.
