Very Short Questions
2) What is the cause of refraction of light
3) Define the term 'angle of incidence'
4) what do you understand by the term 'angle of refraction'?
5) Define angle of deviation.
6) What do you understand by the term 'refractive index of a medium'?
7) What is the refractive index of an opaque body ?
8) Which material among the reflective index media has maximum refractive index?
9) What is the refractive index of :
a) vacuum b) water
10) What is the unit of refractive index ?.
11) On what factors does the refractive index of medium depend ?
12) What is the principle of reversibility of light ?
13) How the angle incidence (i), angle of emergence (e), angle of prism (A) and angle of deviation (δ) are related to each other ?
14) What is the relation between the angle of incidence i in the air and the angle of refraction r in the glass ?
15) What do you understand by the term 'lateral displacement'?
16) Does total internal reflection occurs when light passes from a rather medium to a denser medium?
17) Define prism.
18) A light ray is incident from a denser medium on the boundary separating it from a rarer medium at an angle of incidence equal to the critical angle. What is the angle of refraction for the ray?
19) State the approximate value of the critical angle for glass-air surface.
20) Define the critical angle.
21) Write down a relation between the refractive index and the critical angle.
22) States Snell's law of refraction.
23) What is the angular deviation of the emergence ray from the glass block with respect to the incident ray ?
24) a) What is an optical fibre ?
b) give one practical use of optical fibre.
Short Questions:
1) State the law of refraction.
2) Define absolute refractive index of a medium.
3) The refractive index of water with respect to air is ₐμₕ and that of glass with respect to air ₐμₕ. Express the refractive index of glass with respect to water.
4) How is the refractive index of a medium is related to the speed of light in it ? For which colour of white light, the refractive index of a transparent medium is the least ?
5) Distinguish between the ordinary reflection and total internal reflection.
a) reflection takes place from a polished surface, when the rays travel from a rarer medium to a denser medium.
6) Give reasons why:
a) why do stars twinkle ?
b) why the planet is do not Twinkle ?
c) State and explain Snell's law of the reflection of light.
7) What two conditions must be fullfilled for the total internal reflection of light to occur ?
8) What should be the ratio the speed of light through the liquid to the speed through glass so that there is no refraction of light at the boundaries of the glass block when the system is illuminated by light of one colour ?
9) State two advantages of using a right angled prism as a reflector, rather than a plane mirror..
10) Explain briefly what causes the twinkling of stars at night.
11) a) What is meant by refraction ?
b) Express the refractive index n of a medium:
i) in terms of velocity of light
ii) in terms angle of incidence i in air and the angle of refraction r in a danser medium.
c) 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)?
Questions Based On Diagrams
1) Draw a ray diagram to illustrate has a ray of light incidence obliquely on one face of a rectangular glass slab of uniform thickness emerges parallel to its original direction. Mention which pairs of angles are equal.
2) Draw diagram to show the refraction of light from
a) air to glass glass
b) glass to air.
In each diagram, label the incidence ray, refracted rays, the angle of incidence (i) and the angle of refraction (r).
3) a) Copy the diagram given below and show clearly the path of the ray, through the glass slab, till it emerges out in air. In the diagram, clearly show
i) angle of incidence
ii) angle of refraction
iii) angle of emergence
b) How is angle of incidence related to angle of emergence ?
c) On the diagram clearly show the lateral displacement.
a) The complete labelled diagram is in shown in which i is the angle of incidence, r is the angle of refraction and e is the angle of emergence .
b) Angle of incidence is equal to the angle of emergence
c) lateral displacement is equals to XY
4) Figure shows a point source P inside a water container. Three rays A, B and C starting from P are shown upto the water surface, Show in the diagram the path of these rays after striking the water surface. The critical angle for water air PR is 48°.
5) a) A ray of monochromatic light enters glass PQRS as shown in figure. Complete the path of rays till it emerges from the glass. Critical angle of glass is 42°.
b) Draw a neat diagram of a prismatic periscope.
c) What are the advantages of total internal reflecting prism over plane mirror?
6) a) Copy the following diagram and complete it to show the rays emerging out of the prism B.
b) State the principal used for the completing your ray diagram.
7) By the drawing a diagram show:
Why does a stick immersed partially obliquely in water appear bent and short?
8) Why a coin placed in water tank appears raised ?
9) Why are not the stars exactly the same position, where they appear to the eye ?
10) Why does a tank filled with water appear shallow?
11) A student puts his pencil into an empty trough. What changes will be observed in appearance of the pencil. When water is poured into the trough ? The student observes the pencil through the water from the position indicated in the diagram.
12) Name the phenomena which accounts for the above stated observation. Complete the diagram showing how the student's eye sees the pencil through the water .
13) During the sunset and sunrise, the Sun is seen even when it is slightly below the horizon. Explain the reason.
Or
Why does the sun appear bigger during sunset or sunrisethe ?
14) Figure shows two rays of light OP and OQ coming from an object at the bottom of a pond, incidence on the water surface.
a) Mark on the diagram:
i) the angle of incidence of ray OP.
ii) the angle of refraction of ray OP
iii) the position of image of the object as seen from above.
A) FILL IN THE BLANKS:
1. When a ray of light of light travelling obliquely in a____ medium, enters a denser medium. It always bends___ the normal.
2. When a ray of light of light travelling obliquely in a denser medium, enters a_____ medium, it always bends away from the____.
3. When a ray of light strikes the surface of separations of two optical media at right angles, it__ suffer any______. does
4. Total internal reflection occurs when a ray of light passes from a ____medium to a____ medium.
5. For total internal reflection angle of incidence in the denser medium should be_____ then critical angle.
6. Sine of critical angle= ___.
7. Critical angle is the angle of the angle of____ for which the angle of_____ is____.
8. μ = Velocity of light in _____velocity of light in a _____.
9) sin r= sin i/___ .
10. Angle of deviation is the angle which the____ ray makes with the ___ ray.
11) The twinkling star is due to_____.
B) STATE whether true or false. Also correct the false statements
1. When a ray of light passes from one medium to another, its direction does not change but the frequency changes.
2. If the angle of incidence is less than Critical Angle, light is not refracted at all when it falls on the surface from a denser medium to a rare rare medium.
3. When a Ray of light travels from a rarer medium to a denser medium, it bends away from the normal.
4. Lateral displacement decreases with the increase in thickness of the medium and with the increase in angle of incidence.
5. The refracted ray inside a prism travels perpendicular to the base if the prism is equilateral.
6. If the refractive index of glass with respect to air is 4/3, the refractive index of air with respect to class will also be 4/3.
7. Refractive index of red light greater than that of violet light.
8. The critical angle for a pair of media is less for red light and more for violet light.
9. A total reflecting prism used to deviate a ray of light through 80° and 180°.
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