why prisms are used in binoculars ? with brief explanation
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Telescopes and binoculars are used to view distant objects.
They consist of a long tube with a big convex lens (objective lens) and a small convex lens called eye piece. The ratio of
focal length of objective to that of eye piece gives us the magnification.
The image appears inverted when we view it. Length of telescope is the sum of focal lengths of
two lenses.
To make the image erect (not inverted) for our eye, we need to add another inverting lens in the middle of the two lenses. This further increases the length of the telescope by 4 times the length of the inverting lens.
For obtaining a good view of distant objects, the size of telescope has to be very big in diameter and in length too. They are heavy and cannot be conveniently handled.
Prismatic telescopes solve this problem by use of two triangular prisms to invert the image between the eye piece lens and the objective lens. The first prism receives parallel rays from distant objects and reflects (total internal reflection) rays on to another prism which totally internally reflects rays back towards the eye piece. These rays are now viewed through eye piece with a large magnification.
In SLR cameras and binoculars, prisms are used along with a reflector mirror (concave). This is when you see that the binocular is not cylindrical in shape.
To make the image erect (not inverted) for our eye, we need to add another inverting lens in the middle of the two lenses. This further increases the length of the telescope by 4 times the length of the inverting lens.
For obtaining a good view of distant objects, the size of telescope has to be very big in diameter and in length too. They are heavy and cannot be conveniently handled.
Prismatic telescopes solve this problem by use of two triangular prisms to invert the image between the eye piece lens and the objective lens. The first prism receives parallel rays from distant objects and reflects (total internal reflection) rays on to another prism which totally internally reflects rays back towards the eye piece. These rays are now viewed through eye piece with a large magnification.
In SLR cameras and binoculars, prisms are used along with a reflector mirror (concave). This is when you see that the binocular is not cylindrical in shape.
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Answer:
1. If 2 telescopes are mounted parallel to each other so that an object can be seen by both the eyes simultaneously the arrangement is called binocular.
2. The length of each tube is reduced by using a set of totally reflecting prisms.
3. They provide intense, erect image free from lateral inversion.
f0-focal length of objective
fe- focal length eyepiece
4. Through a binocular we get 2 images of the same object from different angles at same time.
5. Their super position gives the perception of depth also with length and breadth.
6. Binocular vision gives proper 3D image.
7. By using total reflecting prisms there is no loss of intensity.
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