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प्रश्न
Answer the following question.
Why is prism binoculars preferred over traditional binoculars? Describe its working in brief.
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उत्तर
- Traditional binoculars use only two cylinders. Distance between the two cylinders can’t be greater than that between the two eyes. This creates a limitation of the field of view.
- A prism binocular has two right-angled glass prisms that apply the principle of total internal reflection.
- The incident light rays are reflected internally twice giving the viewer a wider field of view. For this reason, prism binoculars are preferred over traditional binoculars.
Working:
Prism binoculars
- The prism binoculars consist of 4 isosceles, right-angled prisms of a material having a critical angle less than 45°.
- The prism binoculars have a wider input range compared to traditional binoculars.
- The light rays incident on the prism binoculars, first get total internally reflected by the isosceles, right-angled prisms 1 and 4.
- These reflected rays undergo another total internal reflection by prisms 2 and 3 to form the final image.
APPEARS IN
संबंधित प्रश्न
Which colour of light has a higher critical angle? Red light or green light.
What do you understand by the deviation produced by a prism? Why is it caused?
A light ray does not bend at the boundary in passing from one medium to the other medium if the angle of incident is ______.
In the given figure PQ and PR are the two light rays emerging from an object P. The ray PQ is refracted as QS.
- State the special name given to the angle of incidence ∠PQN of the ray PQ.
- What is the angle of refraction for the refracted ray QS?
- Name the phenomenon that occurs if the angle of incidence ∠PQN is increased.
- The ray PR suffers partial reflection and refraction on the water-air surface. Give reason.
- Draw in the diagram the refracted ray for the incident ray PR and hence show the position of image of the object P by the letter P’ when seen vertically from above.
The observation made by Swarali while doing the experiment is given below. Based on these write answers to the questions:
Swarali found that the light ray travelling from the denser medium to rarer medium goes away from the normal. If the angle of incidence (i) is raised by Swarali, the angle of refraction (r) went on increasing. However, after certain value of the angle of incidence the light ray is seen to return back into the denser medium.
Questions:
- What is the specific value of∠i called?
- What is the process of reflection of incident rays into denser medium called?
- Draw the diagrams of three observations made by Swarali.
(i) Define critical angle.
(ii) State one important factor which affects the critical angle of a given medium.
Plot a graph between
Sine of angle of incidence versus sine of angle of refraction,
In the following figure, show two rays A and B travelling from water to air. If the critical angle for water- air surface is 48°, complete the ray diagram showing the refracted rays for each. State conditions when the ray will suffer total internal reflection.
Name the principle on the basis of which optical fibres work.
Why do diamonds sparkle?
Images formed by totally reflecting prisms are brighter than the image formed by ordinary reflected light, why?
Name the factors affecting the critical angle for the pair of media.
What is meant by the statement, ‘the critical angle for diamond is 24°’?
The diagram shows a point source P inside a water container. Three rays A, B, and C starting from P are shown up to the water surface. Show in the diagram the path of these rays after striking the water surface. The critical angle for the water-air pair is 48°.
The adjacent diagram shows two right-angled isosceles prisms A and B. Complete the diagram to show the path of rays P and Q emerging out of the prism B. What principles have you used to complete the diagram?
Choose the correct option.
Angles of deviation for extreme colours are given for different prisms. Select the one having maximum dispersive power of its material.
Which of the following is not involved in formation of a rainbow?
Total internal reflection can take place only if light is travelling from ______.
Optical fibre communication uses the principle of ______.
The outer concentric shell in optic fiber is called ______.
Which of the following statements about total internal reflection is true?
A green light is incident from the water to the air-water interface at the critical angle (θ). Select the correct statement.
A ray of light incident at an angle θ on a refracting face of a prism emerges from the other face normally. If the angle of the prism is 5° and the prism is made of a material of refractive index 1.5, the angle of incidence is ______.
The phenomena involved in the reflection of radiowaves by ionosphere is similar to ______.
Observe the given figure of the raindrop and answer the following questions:
- Label A and B of the given diagram. Why colour will deviate most.
- Name the phenomenon shown in label C.
An endoscope uses optic fiber to transmit high resolution images of internal organs without loss of information. The principle of light that is used by the optic fiber is based on ______.
