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प्रश्न
Why do diamonds sparkle?
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उत्तर
Critical angle for diamond is quite less and is only 24°. Besides these diamonds are cut very sharp, making a large number of the refracting surfaces. Hence when a ray of light enters a diamond, it suffers a series of total internal reflections on account of a very small critical angle. This makes a ray of light literally trapped within the diamond for a little time and this trapped light energy makes a diamond sparkle.
संबंधित प्रश्न
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.
Plot a graph between
Angle of incidence versus angle of refraction.
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.
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?
Complete the following diagram to show the path of the ray of a single colour in the diagram as if enters in and emerges out of the prism. Mark the angles wherever necessary. (Critical angle for glass = 42°).
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.
The angle made by incident ray of light with normal of the reflecting surface is called ______.
- Assertion (A): Propagation of light through an optical fibre is due to total internal reflection taking place at the core-cladding interface.
- Reason (R): Refractive index of the material of the cladding of the optical fibre is greater than that of the core.
Name any two phenomena which take place in the formation of a rainbow.
