Advertisements
Advertisements
Question
(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?
Advertisements
Solution
Note : here that when the angle of incidence in the denser medium is more than the critical angle (= 42), then the ray undergoes total internal reflection.
At angle of incidence equal to critical angle, the ray grazes the interface.
(b) Diagram of prism periscope:
(c) In case of reflection from plane mirror, all of light in not reflected. In case of total reflecting prism, all rays failing beyond critical angle will be totally reflected. The intensity of reflected light is equal to the intensity of incident light in case of total internal ref;lection but not in case of reflection from plane mirror.
In addition, the reflection through a thick mirror causes multiple image formation as well as lateral inversion of image.
Due to the above two reasons, the total reflecting prisms are preferred over the plane mirrors.
APPEARS IN
RELATED QUESTIONS
What is total internal reflection?
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 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].
Plot a graph between
Angle of incidence versus angle of refraction.
Images formed by totally reflecting prisms are brighter than the image formed by ordinary reflected light, why?
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
Answer the following question.
Under what conditions are total internal reflection possible? Explain it with a suitable example.
Which one of the following is NOT the correct formula for refractive index of glass w.r.t. air (aμg) (i = angle of incidence, r = angle of refraction)
The critical angle is defined as the angle of incidence at which the total internal reflection starts to occur.
