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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.
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संबंधित प्रश्न
A ray of light travels from water to air as shown in the diagram given below :
1) Copy the diagram and complete the path of the way. Given the critical angle for water is 48°.
2) State the condition so that internal reflection occurs in the above diagram.
The diagram below shows a point source P inside a water container. Four rays A, B, C, D starting from the source 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 surface is 48°.
- Name the phenomenon which the rays B and D exhibit.
Name two factors which affect the critical angle for a given pair of media. State how do the factors affect it.
Two isosceles right-angle glass prisms P and Q are placed near each other as shown in Fig. Complete the path of the light ray entering the prism P till it emerges out of the prism Q.
Solve the previous problem if the paperweight is inverted at its place so that the spherical surface touches the paper.
(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,
State two advantages of using a right-angle prism as a reflector, rather than a plane mirror.
State one factor on which a critical angle for a given pair of media depends. The critical angle for the glass-air interface is 45° for the yellow light. Will it be equal to, less than or greater than 45° for (i) red light, (ii) blue light?
What is meant by the term ‘critical angle’?
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°.
PQ and PR are two light rays emerging from the object as shown in the figure below:
(i) What is the special name given to the angle of incidence (∠PQN) of ray PQ?
(ii) Copy the ray diagram and complete it to show the position of the image of the object P when seen obliquely from above.
(iii) Name the phenomenon that occurs if the angle of incidence ∠PQN is increased still further.
Explain ‘mirage’ as an illustration of refraction.
Solve Numerical example.
From the given data set, determine angular dispersion by the prism and dispersive power of its material for extreme colours. nR = 1.62 nV = 1.66, δR = 3.1°
The resultant `vec"R"` of `vec"P"` and `vec"Q"` is perpendicular to `vec"P"`. Also `|vec"P"|=|vec"R"|`. The angle between `vec"P"` and `vec"Q"` is ______.
[tan 45° = 1]
A green light is incident from the water to the air-water interface at the critical angle (C). Select the correct statement.
For the same angle of incidence, the angle of refraction in four media A, B, C and D are 25°, 30°, 35° and 40° respectively. The speed of light is least in medium ______.
For total internal reflection to take place, the angle of inddence i and the refractive index µ of the medium must satisfy the inequality ____________.
The angle of minimum deviation produced by a thin glass prism in air is 'δ'. If that prism is immersed in water, the angle of minimum deviation will be ______.
( aμg = refractive index of glass w.r.t, air aμw = refractive index of water w.r.t. air)
For a ray of light, the critical angle is minimum when it travels from ______.
Total internal reflection can take place only if light is travelling from ______.
The critical angle is defined as the angle of incidence at which the total internal reflection starts to occur.
What is the phenomenon used in optical fiber? Explain.
State the condition under which total internal reflection occurs. Give the mathematical expression for total internal reflection.
A Rainbow is a beautiful natural phenomenon formed because of the following:
A ray of light passes from vacuum into a medium of refractive index µ, the angle of incidence is found to be twice the angle of refraction. Then the angle of incidence is ______.
A given ray of light suffers minimum deviation in an equilateral prism P. Additional prism Q and R of identical shape and of the same material as P are now added as shown in the figure. The ray will now suffer ______.
State two differences between normal reflection and total internal reflection.
