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प्रश्न
Answer the following question.
Under what conditions are total internal reflection possible? Explain it with a suitable example.
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उत्तर
Conditions for total internal reflection:
- The light ray must travel from denser medium to rarer medium.
- The angle of incidence in the denser medium must be greater than critical angle for the given pair of media.
Total internal reflection in optical fibre:
- Consider an optical fibre made up of the core of refractive index n1 and cladding of refractive index n2 such that, n1 > n2.
- When a ray of light is incident from a core (denser medium), the refracted ray is bent away from the normal.
- At a particular angle of incidence ic in the denser medium, the corresponding angle of refraction in the rarer medium is 90°.
- For angles of incidence greater than ic, the angle of refraction becomes larger than 90° and the ray does not enter into the rarer medium at all but is reflected totally into the denser medium as shown in the figure.
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संबंधित प्रश्न
State the conditions required for total internal reflection of light to take place.
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.
State the relation between the critical angle and the absolute refractive index of a medium.
Draw the diagram of a right-angled isosceles prism which is used to make an invented image erect.
A light ray does not bend at the boundary in passing from one medium to the other medium if the angle of incident is ______.
State two conditions necessary for total internal reflection to occur.
Prove the statement.
A rainbow is the combined effect of the refraction, dispersion, and total internal reflection of light.
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.
i) Observe the given figure and answer the following questions.
a) Identify and write the natural process shown in the figure.
b) List the phenomena which are observe in this process.
c) Redraw the diagram and show above phenomena in it.
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].
Define critical angle for a given medium.
Plot a graph between
Angle of incidence versus angle of reflection,
Plot a graph between
Angle of incidence versus angle of refraction.
If a light ray does not undergo, refraction at the boundary between two media, the angle of incidence is:
Name the principle on the basis of which optical fibres work.
How does a ray of light bend when it travels from when it is normal to the interface of the two media.
How are critical angles related to the refractive index of the medium?
Images formed by totally reflecting prisms are brighter than the image formed by ordinary reflected light, why?
A ray of light incident at an angle of incidence ‘i’ passes through an equilateral glass prism such that the refracted ray inside the prism is parallel to its base and emerges from the prism at an angle of emergence ‘e’.
What can you say about the value of the angle of deviation in such a situation?
Name the factors affecting the critical angle for the pair of media.
What is meant by the term ‘critical angle’?
Choose the correct option.
Consider the following phenomena/ applications: P) Mirage, Q) rainbow, R) Optical fibre and S) glittering of a diamond. Total internal reflection is involved in
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.
Answer the following question.
Define the critical angle of incidence and obtain an expression for it.
What are the conditions to achieve total internal reflection?
Write any two uses of total internal reflection.
A rectangular block of glass ABCD has a refractive index 1.6. A pin is placed midway on the face AB (Figure). When observed from the face AD, the pin shall ______.
- appear to be near A.
- appear to be near D.
- appear to be at the centre of AD.
- not be seen at all.
A Rainbow is a beautiful natural phenomenon formed because of the following:
Small air bubbles rising up a fish tank appear silvery when viewed from some particular angle is due to the ______.
