REFRACTION AT PLANE SURFACES
Brief Revision - Important Question Solving:
Frequently Tested Topics:
Critical angle- definition and concept
Laws of Refraction
Relation between critical angle and refractive index
Factors affecting refractive index, lateral displacement, shift, angle of deviation, critical angle.
Completing the path of the ray through prisms
*Note that other aspects of the chapter are equally important.
Important Past Questions:
Define critical angle.
State the conditions for total internal reflection to take place.
State the factors which affect the critical angle for a given medium.
State the laws of refraction of light.
State the relation between critical angle and absolute refractive index for a medium.
(2008, 2012, 2018)
i) What is the relation between the refractive index of water with respect to air (aμw) and the refractive index of air with respect to water (wμa)?
ii) If the refractive index of water with respect to air is 5/3, calculate the refractive index of air with respect to water.
i) Why is the ratio of the velocities of light of wavelengths 4000 Å and 8000 Å in vacuum 1:1?
ii) Which of the above wavelengths has a higher frequency?
Which colour of light has a higher critical angle: red light or green light?
How is the refractive index of a material related to real and apparent depth?
(2007, 2011, 2017)
How is refractive index related to velocity of light in vacuum/air and velocity of light in a given medium?
A boy uses blue colour of light to find the refractive index of glass. He then repeats the experiment using red colour of light. Will the refractive index be same or different in the two cases? Give reason. [IMPORTANT}
State the dependence of angle of deviation on:
i) Refractive index of the material of the prism (2016)
ii) Wavelength of light (2009, 2016)
iii) Value of angle of incidence. Draw a graph showing the variation in angle of deviation with the angle of incidence at a prism surface. (2009, 2019)
Name one factor that affects the lateral displacement of light as i t passes through a rectangular glass slab.
The speed of light in glass is 2 x 10^5 km/s. What is the refractive index of glass?
A ray of light passes from water to air. How does the speed of light change?
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?
Define the term refractive index in terms of velocity of light.
What is the cause of refraction of light?
The refractive index of diamond is 2.42. What is meant by this statement?
i) A monochromatic beam of light of wavelength λ passes from air into a glass block. Write an expression to show the relation between speed of light in air and the speed of light in glass.
ii) As the ray of light passes from air to glass, state how the wavelength of light changes. Does it increase, decrease, or remain constant?
Mention one difference between reflection of light from a plane mirror and total internal reflection of light from a prism.
When a ray of light enters from one medium to another having different optical densities, it bends. Why does this phenomenon occur? Write one condition where it does not bend when entering a medium of different optical density.
Can the absolute refractive index of a medium be less than one?
A coin placed at the bottom of a beaker appears to be raised by 4.0cm. If the refractive index of water is 4/3, find the depth of the water in the beaker.
Does the depth of a tank of water appear to change or remain the same when viewed normally from above?
Write a relation between the angle of incidence (i), angle of emergence (e), angle of prism (A) and angle of deviation (d) for a ray of light passing through an equilateral prism.
DIAGRAM BASED QUESTIONS
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)
Copy the diagram given below and complete the path of light ray till it emerges out of the prism. The critical angle of glass is 42. In your diagram mark the angles wherever necessary.
Draw the diagram given below and clearly show the path taken by the emergent ray.
A ray of light is moving from a rarer medium to a denser medium and strikes a plane mirror placed at 90 degree to the direction of the ray as shown in the diagram.
(i) Copy the diagram and mark arrows to show the path of the ray of light after it is reflected from the mirror.
(ii) Name the principle you have used to mark the arrow to show the direction of the ray.
A ray of light moves from a rare medium to a dense medium as shown in the diagram below. Write down the number of the ray which represents the partially reflected ray.
In the diagram below, PQ is a ray of light incident on a rectangular glass block.
(i) Copy the diagram and complete the path of the ray of light through the glass block. In your diagram, mark the angle of incidence by letter ‘i’ and the angle of emergence by the letter ‘e’.
(ii) How are the angles ‘i’ and ‘e’ related to each other?
A ray of monochromatic light enters a liquid from air as shown in the diagram given below:
(i) Copy the diagram and show in the diagram the path of the ray of light after it strikes the mirror and reenters the medium of air.
(ii) Mark in your diagram the two angles on the surface of separation when the ray of light moves out from the liquid to air.
A ray of light enters a glass slab PQRS, as shown in the diagram. The critical angle of the glass is 42°. Copy this diagram and complete the path of the ray till it emerges from the glass slab. Mark the angles in the diagram wherever necessary.
A ray of light XY passes through a right angled isosceles prism as shown below: (i) What is the angle through which the incident and deviates and emerges out of the prism?
(ii) Name the instrument where this action of prism is put into use.
(iii) Which prism surface will behave as a mirror?
A ray of light travels from water to air as shown in the diagram given.
(i) Copy the diagram and complete the path of the ray. Given the critical angle for water is 48 degree.
(ii) State the condition so that total internal reflection occurs in the diagram.
A ray of light PQ is incident normally on the hypotenuse of a right angled prism ABC as shown in the diagram given alongside:
(i) Copy the diagram and complete the path of the ray PQ till it emerges from the
(ii) What is the value of the angle of deviation of the ray?
(iii) Name an instrument where this action of the prism is used.
A stick partly immersed in water appears to be bent. Draw a ray diagram to show the bending of the stick when placed in water and viewed obliquely from above.
Two parallel rays of Red and Violet travelling through air, meet the air-glass boundary as shown in the figure:
i) Will their paths inside the glass be parallel? Give a reason for your answer. ii) Compare the speeds of the two rays inside the glass.
i) The diagram below shows a ray of white light PQ coming from an object P and incident on the surface of a thick glass plane mirror. Copy the diagram and complete it to show the formation of three images of the object P as formed by the mirror.
ii) Which image will be the brightest image?
The diagram shows a point source P inside a water container. Four rays A, B, C, D starting from the source P are shown up to the water surface.
i) Show in the diagram the path of these rays after striking the water surface. The critical angle for water air surface is 48 degree.
(ii) Name the phenomenon which the rays B and D exhibit.
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 strikes the surface of a rectangular glass block such that the angle of incidence is
Sketch a diagram to show the approximate path taken by the ray in each case as it passes through the glass block and emerges from it.
A ray of monochromatic light is incident from air on a glass slab:
(i) Draw a labelled ray diagram showing the change in the path of the ray till it emerges from the glass slab.
(ii) Name the two rays that are parallel to each other.
(iii) Mark the lateral displacement in your diagram.
Draw a labelled ray diagram to illustrate:
(1) Critical angle (2) Total internal reflection,
for a ray of light moving from one medium to another.
Jatin puts a pencil into a glass container having water and is surprised to see the pencil in a different state.
(i) What change is observed in the appearance of the pencil?
(ii) Name the phenomenon responsible for the change.
(iii) Draw a ray diagram showing how the eye sees the pencil.
Light passes through a rectangular glass slab and through a triangular glass prism. In what way does the direction of the two emergent beams differ and why?
With the help of a well-labelled diagram show that the apparent depth of an object, such as a coin, in water is less than its real depth.