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प्रश्न
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.
उत्तर
The necessary conditions for total internal reflection to occur are
- Light must travel from a denser medium to a rarer medium.
- The angle of incidence must be greater than the critical angle.
In this case, the angle of incidence. ∠ i > 48°
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संबंधित प्रश्न
Draw the diagram of a right-angled isosceles prism which is used to make an invented image erect
Name two factors which affect the critical angle for a given pair of media. State how do the factors affect it.
Swarali has got the following observations while doing an experiment. Answer her questions with the help of observations.
Swarali observed that the light bent away from the normal, while travelling from dense medium to rarer medium. When Swarali increased the values of angle of incidence (i), the values of angle of refraction (r) went on increasing. But at a certain angle of incidence, the light rays returned into the dense medium.
So, Swarali has some questions. Answer them –
a) Name this certain value of ‘i ’. What is the value of ‘r’ at that time ?
b) Name this process of returning of light in dense medium. Explain the process.
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.
The diagram below shows a light source P embedded in a rectangular glass block ABCD of critical angle 42°. Complete the path of the ray PQ till it emerges out of the block. [Write necessary angles].
(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?
What is meant by the statement, ‘the critical angle for diamond is 24°’?
How is the critical angle of a material related to its refractive index?
A ray of light passes through a right-angled prism as shown in the figure. State the angles of incidence at the faces AC and BC.
Answer the following question.
Define the critical angle of incidence and obtain an expression for it.
