Advertisements
Advertisements
प्रश्न
Solve Numerical example.
From the given data set, determine angular dispersion by the prism and dispersive power of its material for extreme colours. nR = 1.62 nV = 1.66, δR = 3.1°
Advertisements
उत्तर
Given: nR = 1.62, nV = 1.66, δR = 3.1°
To find: i. Angular dispersion (δVR)
ii. Dispersive power (ωVR)
Formula: i. δ = A (n − 1)
ii. δVR = δV − δR
iii. ω = `(δ_"V"-δ_"R")/(((δ_"V"+δ_"R")/2))`
Calculation: From formula (i),
δR = A(nR − 1)
∴ A = `δ_"R"/(("n"_"R"-1))=3.1/((1.62-1))=3.1/0.62`
∴ δV = A(nV − 1) = 5 × (1.66 − 1) = 3.3°
From formula (ii),
δVR = 3.3 − 3.1 = 0.2°
From formula (iii),
ωVR = `(3.3-3.1)/(((3.3+3.1)/2))=0.2/6.4xx2=0.2/3.2=1/16`
= 0.0625
- Angular dispersion by prism is 0.2°
- Dispersive power of material of prism is 0.0625.
APPEARS IN
संबंधित प्रश्न
You are given prisms made of crown glass and flint glass with a wide variety of angles. Suggest a combination of prisms which will
(a) deviate a pencil of white light without much dispersion,
(b) disperse (and displace) a pencil of white light without much deviation.
Draw the diagram of a right-angled isosceles prism which is used to make an invented image erect.
State two conditions necessary for total internal reflection to occur.
Draw diagram to illustrate the total internal reflection.
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.
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.
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:
How does a ray of light bend when it travels from when it is normal to the interface of the two media.
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.
If a ray of light passes from medium I to medium II without any change of direction, what can be said about the refractive indices of these media (angle I is not 0)?
State two advantages of using a right-angle prism as a reflector, rather than a plane mirror.
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?
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?
Name the factors affecting the critical angle for the pair of media.
How is the critical angle of a material related to its refractive index?
Draw a diagram, properly labelled, to illustrate the use of a total reflecting prism (a right-angled isosceles prism) to turn a ray of light through 180°. Name an instrument in which this device is used.
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.
Answer the following question.
Under what conditions are total internal reflection possible? Explain it with a suitable example.
The critical angle is defined as the angle of incidence at which the total internal reflection starts to occur.
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 ______.
Which of the following is used in optical fibres?
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 ______.
