Karnataka Board PUCPUC Science 2nd PUC Class 12

Solve the Previous Problem If the Paperweight is Inverted at Its Place So that the Spherical Surface Touches the Paper. - Physics


Solve the previous problem if the paperweight is inverted at its place so that the spherical surface touches the paper.



Taking the radius of the paperweight as its thickness = 3 cm
Refractive index of the paperweight (μg) = 3/2
Refractive index of the air (μ1) = 1

Image shift is given by: 

\[∆ t = \left( 1 - \frac{1}{\mu} \right)t\] 

\[ = \left( 1 - \frac{2}{3} \right)3\] 

\[ = \left( \frac{1}{3} \right)3\] 

\[   =   1  \text{ cm }\]
The upper surface of the paperweight is flat and the spherical spherical surface is in contact with the printed letter.
Therefore, we will take it as a simple refraction problem.

Hence, the image will appear 1 cm above point A.

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Chapter 18: Geometrical Optics - Exercise [Page 415]


HC Verma Class 11, Class 12 Concepts of Physics Vol. 1
Chapter 18 Geometrical Optics
Exercise | Q 45 | Page 415


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.

State the conditions required for total internal reflection of light to take place

The figure shows a ray of light falling normally on the face AB of an equilateral glass prism having refractive index`3/2`, placed in water of refractive index `4/3`.Will this ray suffer total internal reflection on striking the face AC? Justify your answer.

Draw the diagram of a right-angled isosceles prism which is used to make an invented image erect

A light ray suffers reflection and refraction at the boundary in passing from air to water. Draw a neat labelled ray diagram to show it.

A light ray of yellow colour is incident on an equilateral glass prism at an angel of incidence equal to 48° and suffers minimum deviation by an angle of 36°. (i) What will be the angle of emergence? (ii) If the angle of incidence is changes to (a) 30°, (b) 60°, state whether the angle of deviation will be equal to, less than or more than 36° ? 

Explain the term critical angle with the aid of a labelled diagram. 

A light ray is incident from a denser medium on the boundary separating it from a rarer mediuma an angle of incident equal to the critical angle, what is the angle of refraction for the ray?

Fill in the blanks to complete the following sentence 

critical angle is the angle of ……………. In denser medium for which the angle of ………….. in rarer medium is…………………. 


Write the relation between the refractive index and critical angle for a given pair of optical media?

Calculate the speed of light in a medium whose critical angle is 30° ?

Prove the statement.

A rainbow is the combined effect of the refraction, dispersion, and total internal reflection of light.

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.

Total internal reflection can take place only if ______.

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.


  1. What is the specific value of∠i called?
  2. What is the process of reflection of incident rays into denser medium called?
  3. Draw the diagrams of three observations made by Swarali.

 Define critical angle for a given medium. 

Name the principle on the basis of which optical fibres work.

Can light be ‘piped’ like sound in a doctor’s stethoscope?

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 three actions that a total reflecting prism can produce.

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

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.

Select the WRONG statement.

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.

Which of the following is not involved in formation of a rainbow?

Answer the following question.

Explain ‘mirage’ as an illustration of refraction.

Answer the following question.

Under what conditions are total internal reflection possible? Explain it with a suitable example.

Answer the following question.

Define the critical angle of incidence and obtain an expression for it.

Answer the following question.

Describe the construction and working of an optical fibre.

Answer the following question.

What are the advantages of optical fibre communication over electronic communication?

Answer the following question.

Why is prism binoculars preferred over traditional binoculars? Describe its working in brief.

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?

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°

Observe the given figure and write appropriate phenomenon of light in the box.

Critical angle of light passing from glass to air is maximum for ____________.

The resultant `vec"R"` of `vec"P"` and `vec"Q"` is perpendicular to `vec"P"`. Also `|vec"P"|=|vec"R"|`. The angle between `vec"P"` and `vec"Q"` is ______.
[tan 45° = 1]

A green light is incident from the water to the air-water interface at the critical angle `(theta)`. Select the correct statement

For the same angle of incidence, the angle of refraction in four media A, B, C and D are 25°, 30°, 35° and 40° respectively. The speed of light is least in medium ______.

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)

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 ______.

Optical fibre communication uses the principle of ______.

The twinkling effect of star light is due to ______.

A particle is projected such that the horizontal range and vertical height are equal. Then the angle of projection is :

The entire light is reflected back into the denser medium is called ______.

The outer concentric shell in optic fiber is called ______.

A bundle of glass threads, each of which is capable of transmitting messages using light waves is called ______.

Which of the following statements about total internal reflection is true?

The critical angle is defined as the angle of incidence at which the total internal reflection starts to occur.

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.

Define the critical angle.

Write any two uses of total internal reflection.

What are the examples of total internal reflection in nature?

A green light is incident from the water to the air-water interface at the critical angle (θ). Select the correct statement. 

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 ______.

The phenomena involved in the reflection of radiowaves by ionosphere is similar to ______.

State the condition under which total internal reflection occurs. Give the mathematical expression for total internal reflection.

A Rainbow is a beautiful natural phenomenon formed because of the following:

Observe the given figure of the raindrop and answer the following questions:

  1. Label A and B of the given diagram. Why colour will deviate most.
  2. Name the phenomenon shown in label C.

A ray of light passes through a prism of refractive index `sqrt2` as shown in the figure. Find:

  1. The angle of incidence (∠r2) at face AC.
  2. The angle of minimum deviation for this prism.

A light is entering from one medium refractive index `("RI" =5/3)` to another medium at an angle 30°. The angle of refraction for other medium is sin-1 `(5/6)`. then the increase in angle of incidence is ______ such that the ray of light reflected back into the same medium.

Which of the following is used in optical fibres?

A ray of light passes from vacuum into a medium of refractive index µ, the angle of incidence is found to be twice the angle of refraction. Then the angle of incidence is ______.

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 ______.

The angle made by incident ray of light with normal of the reflecting surface is called ______.

Find the value of θ in the given figure.

  • 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.


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