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प्रश्न
Describe the construction and working of an optical fibre.
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उत्तर
Construction:
- An optical fibre consists of an extremely thin, transparent, and flexible core surrounded by an optically rarer flexible cover called cladding.
- For protection, the whole system is coated by a buffer and a jacket
- The entire thickness of the fibre is less than half an mm.
- Many such fibres can be packed together in an outer cover.
Construction of Optical fiber
Working:
- Working of optical fibre is based on the principle of total internal reflection.
- An optical signal (a ray of light) entering the core suffers multiple total internal reflections before emerging out after several kilometres.
- The optical signal travels with the highest possible speed in the material.
- The emerged optical signal has an extremely low loss in signal strength.
Working of Optical fibre
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संबंधित प्रश्न
State the relation between the critical angle and the absolute refractive index of a medium.
Angle of deviation is the angle which the ______ ray makes with the direction of ______ray.
Total internal reflection occurs only when a ray of light passes from a ______ medium to a ______ medium.
One day Chetan’s mother developed a severe stomach ache all of a sudden. She was rushed to the doctor who suggested for an immediate endoscopy test and gave an estimate of expenditure for the same. Chetan immediately contacted his class teacher and shared the information with her. The class teacher arranged for the money and rushed to the hospital. On realizing that Chetan belonged to a below average income group family, even the doctor offered concession for the test fee. The test was conducted successfully.
Answer the following questions based on the above information:
(a) Which principle in optics is made use of in endoscopy?
(b) Briefly explain the values reflected in the action taken by the teacher.
(c) In what way do you appreciate the response of the doctor on the given situation?
Calculate the speed of light in a medium whose critical angle is 30° ?
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.
Define critical angle for a given medium.
Plot a graph between
Angle of incidence versus angle of refraction.
(a) A ray of monochromatic light enters glass PQRS as shown in the fig. Complete the path of ray till it emerges from the glass. (Critical angle of glass is 420).
(b) Draw diagram of a prism periscope.
(c) What are the advantages of total internal reflecting prism over plane mirror?
Make the correct choices for each of the following :
Total Internal reflection takes place when
(where ∠i = angle of incidence, ∠r = angle of refraction, ∠C = critical angle)
How does a ray of light bend when it travels from denser to rarer medium.
Express the refractive index μ of a medium in terms of the angle of incidence i in air and the angle of refraction r in a denser medium.
What is meant by the term ‘critical angle’?
A ray of light is incident as a normal ray on the surface of separation of two different mediums. What is the value of the angle of incidence in this case?
Observe the given figure and write appropriate phenomenon of light in the box.
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)
The entire light is reflected back into the denser medium is called ______.
Optical Fibres are based on the phenomenon of dispersion.
What is the phenomenon used in optical fiber? Explain.
What are the examples of total internal reflection in nature?
A green light is incident from the water to the air-water interface at the critical angle (θ). Select the correct statement.
The angle made by incident ray of light with normal of the reflecting surface is called ______.
Find the value of θ in the given figure.
Small air bubbles rising up a fish tank appear silvery when viewed from some particular angle is due to the ______.
When a ray of light is refracted from one medium to another, then the wavelength changes from 6000 Å to 4000 Å. The critical angle for the interface will be ______.
