Question

Why is a prism binoculars preferred over traditional binoculars? Describe its working in brief.

Answer 1

Hint: Prism has light bending qualities and hence can be used to make corrections and moreover they are also helpful in reducing the length of the instrument. Therefore preferring prism binoculars is more beneficial.

Complete step by step solution
Binoculars: They are also called field glasses and are two telescopes mounted side-by-side and aligned to point in the same direction, allowing the viewer to use both eyes when viewing distant objects.
Prism: It is a solid geometric figure whose two ends are similar as well as equal, and parallel rectilinear figures, with parallelogram sides.
Prism binoculars are used in binoculars because they
Produce an erect right-way facing image
Allows for a compact binocular convenient for hand-held use.
Reduce as much light as possible.
its designs have the added benefit of folding the optical path so that the physical length of the binoculars is less than the focal length of the objective.
It’s principle is that it divides the beam of light into two then brings them together again.
There are two types of prism binoculars :
1. Porro prism binoculars
2. Roof prism binoculars

Working of prism binoculars
At each end of the binocular two objective lenses are situated. The main purpose of the objective lens is to collect light from the object (that the user is looking at) and bring the collected light into focus in the eyepiece lens, which creates a magnified and visible image. Now the image which is generated is backwards and upside down. So prisms are used to fix this problem and they are situated between the objective lens and the eyepiece lens. The prisms used in binoculars are simply glass blocks that act like mirrors. The prisms use internal reflections to bring the beam of light from the objective lens closer together and to correct the orientation of the image created by the objective lens.

Note
Porro prism binoculars use an offset arrangement to line up the objective lens with the eyepiece lens and hence offers a wider view of view than compared to roof prism binoculars.
Roof prisms make it possible to produce small and light binoculars. The principle behind roof prism binoculars is that the beam of light is divided into two and brought together again. This process results in a phenomenon known as phase shifting. In this type of binoculars contrast decrease is observed.