Advertisements
Advertisements
प्रश्न
Answer the following question.
Under what conditions are total internal reflection possible? Explain it with a suitable example.
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.
APPEARS IN
संबंधित प्रश्न
State the conditions required for total internal reflection of light to take place
A light ray does not bend at the boundary in passing from one medium to the other medium if the angle of incident is ______.
Name two factors which affect the critical angle for a given pair of media. State how do the factors affect it.
Draw diagram to illustrate the total internal reflection.
Two isosceles right-angle glass prisms P and Q are placed near each other as shown in Fig. Complete the path of the light ray entering the prism P till it emerges out of the prism Q.
Prove the statement.
A rainbow is the combined effect of the refraction, dispersion, and total internal reflection of light.
Solve the previous problem if the paperweight is inverted at its place so that the spherical surface touches the paper.
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.
(i) Define critical angle.
(ii) State one important factor which affects the critical angle of a given medium.
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 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)
The diagram shows a point source P inside a water container. Three rays A, B, and C starting from P are shown up to the water surface. Show in the diagram the path of these rays after striking the water surface. The critical angle for the water-air pair is 48°.
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 ray of light is incident on a glass surface at an angle of 50° with the corresponding angle of refraction 30°. Find the value of the R.I. of glass.
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?
Answer the following question.
What are the advantages of optical fibre communication over electronic communication?
A green light is incident from the water to the air-water interface at the critical angle `(theta)`. Select the correct statement
For a ray of light, the critical angle is minimum when it travels from ______.
Total internal reflection can take place only if light is travelling from ______.
A particle is projected such that the horizontal range and vertical height are equal. Then the angle of projection is :
Optical Fibres are based on the phenomenon of dispersion.
The angle of incidence at which the angle of refraction is Q£ is called the critical angle.
What are the examples of total internal reflection in nature?
A ray of light incident at an angle θ on a refracting face of a prism emerges from the other face normally. If the angle of the prism is 5° and the prism is made of a material of refractive index 1.5, the angle of incidence is ______.
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 given ray of light suffers minimum deviation in an equilateral prism P. Additional prism Q and R of identical shape and of the same material as P are now added as shown in the figure. The ray will now suffer ______.
- 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.
The diagram below shows a fish in the tank and its image seen in the surface of water.
Name the phenomenon responsible for the formation of this image.
