Advertisements
Advertisements
प्रश्न
State two conditions necessary for total internal reflection to occur.
Write the two conditions for total internal reflection of light.
State the conditions required for total internal reflection of light to take place.
State the two conditions under which total internal reflection occurs.
Advertisements
उत्तर
- The light must travel from a denser medium to a rarer medium.
- The angle of incidence must be greater than the critical angle for the pair of media.
Notes
Students should refer to the answer according to their questions.
APPEARS IN
संबंधित प्रश्न
Draw the diagram of a right-angled isosceles prism which is used to make an invented image erect.
Draw diagram to illustrate the total internal reflection.
Total internal reflection occurs only when a ray of light passes from a ______ medium to a ______ medium.
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.
Write the relation between the refractive index and critical angle for a given pair of optical media?
One day Chetan’s mother developed a severe stomach ache all of a sudden. She was rushed to the doctor who suggested for an immediate endoscopy test and gave an estimate of expenditure for the same. Chetan immediately contacted his class teacher and shared the information with her. The class teacher arranged for the money and rushed to the hospital. On realizing that Chetan belonged to a below average income group family, even the doctor offered concession for the test fee. The test was conducted successfully.
Answer the following questions based on the above information:
(a) Which principle in optics is made use of in endoscopy?
(b) Briefly explain the values reflected in the action taken by the teacher.
(c) In what way do you appreciate the response of the doctor on the given situation?
Calculate the speed of light in a medium whose critical angle is 30° ?
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.
Solve the previous problem if the paperweight is inverted at its place so that the spherical surface touches the paper.
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].

If a light ray does not undergo, refraction at the boundary between two media, the angle of incidence is:
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)
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’.
How is the angle of emergence ‘e’ related to the angle of incidence ‘i’?
PQ and PR are two light rays emerging from the object as shown in the figure below:

(i) What is the special name given to the angle of incidence (∠PQN) of ray PQ?
(ii) Copy the ray diagram and complete it to show the position of the image of the object P when seen obliquely from above.
(iii) Name the phenomenon that occurs if the angle of incidence ∠PQN is increased still further.
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?
A spherical marble, of refractive index 1.5 and curvature 1.5 cm, contains a tiny air bubble at its centre. Where will it appear when seen from outside?
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.
Solve Numerical example.
A monochromatic ray of light is incident at 37° on an equilateral prism of refractive index 3/2. Determine angle of emergence and angle of deviation. If angle of prism is adjustable, what should its value be for emergent rays to be just possible for the same angle of incidence?
The outer concentric shell in optic fiber is called ______.
The critical angle is defined as the angle of incidence at which the total internal reflection starts to occur.
What is a mirage? How does it occur?
Write any two uses of total internal reflection.
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 ______.
Observe the given figure of the raindrop and answer the following questions:

- Label A and B of the given diagram. Why colour will deviate most.
- Name the phenomenon shown in label C.
- 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 on the surface of the water.

Name the phenomenon responsible for the formation of this image.
State two differences between normal reflection and total internal reflection.
When a ray of light is refracted from one medium to another, then the wavelength changes from 6000 Å to 4000 Å. The critical angle for the interface will be ______.
