Question

Overhead projectors are used to show transparencies on a screen. What type of lens does an overhead projector use ?

Answer 1

Hint:This question requires the knowledge of details of overhead projection and the components that are used in the process of projection. Overhead projectors are dependent on transparencies for presenting data on the screen since all data is printed on top of the transparencies.

Complete answer:
The inside of an overhead projector is normally similar to that of a television, with the exception that it has two mirrors. A light and a spare bulb are included in the machine. The bulb transmits light beams to the first mirror, which is caught by the second mirror and led to a magnifying window at the far end of the light path, which focuses the light to maintain the data on the screen.

The “fresnel lens,” which is used in overhead projectors, is modelled after the optics of a microscope and telescope. These lenses are circular, focusing light in one direction, in this case to an area of a reflecting mirror, which subsequently reflects the document on the screen. The optics of the lenses normally invert the pictures; if they don't, a new lens is required.The lenses have a thick centre and thinner borders, which are referred to as convex lenses.

Thus, convex lenses are used in overhead projectors.

Note:The larger lens, known as the objective lens, is closer to the object and produces a smaller image in the scope; nevertheless, the picture or image is too small, necessitating the use of an eyepiece to magnify it. Each lens has a focal length attached to it.The picture is formed in various lenses in such a way that it is formed away from the lenses.