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CBSE Physics (Chapter Wise With Hint / Solution) Class XII

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PHYSICS - CBSE CLASS XII

Optics

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1.When a photon collides with an electron, which of the following characteristics of the
photon increases?

2.Which of the following does not support the wave nature of light?

3.The distance travelled by the ray of light during the time octagonal mirror rotates through 90 ͦ is’L’ if the mirror rotates at N revolution per second, what is the speed of light.

4. A star appear yellow . If it starts accelerating towards earth, how will its colour appears to change.

5.Two points A and B are situated at the same distance from the source of light, but in opposite direction from it.What is the phase difference between the light waves passing through A and B?

6.When the light is polarized by reflection , what is the angle between reflected and refracted rays.

7. For double refracting crystal the refractive indices , for the ordinary and extraordinary denoted by μo and μe. What is the relation valid along the optical axis of the crystal.

8.What is the angle between planes of electric and magnetic field oscillation in case of light waves?

9.What is the colour of the interference fringe nearest to the white central maximum incase of white light?

10. What happens to the fringe pattern when YDS experiment is performed in water instead of air?

11. A man stands in front of a mirror of special shape. He finds that his image has a very small head, a fat body and legs of normal size. What can we say about the shapes of the three arts of the mirror?

12. In which direction relative to the normal, does a ray of light bend, when it enters obliquely a medium in which its speed is increased?

13. For the same angle of incidence, the angles of refraction in three different media A,B and C are 15° ,25° and 35°,respectively. In which medium will the velocity of light be minimum?

14. For what angle of incidence, the lateral shift produced by a parallel sided galss slab is maximum?

15. If a plane glass slab is placed on letters of different colours, the red coloured letters appear more raised up. Why?

16. Does refraction in a water tank make apparent depth same throughout?

17. The critical angle for glass-air interface is ic. Will the critical angle for glass-water interface be greater than or less than ic?

18. An air bubble in a jar of water shines brightly. Why?

19.What happens to the shining of diamond if it is dipped in a transparent oil?

20.What type of a lens is a tumbler filled with water?

21.What type of a lens is an air bubble inside water? Give reason also.

22.A lens immersed in a transparent liquid is not visible. Under what condition can this happen?

23. A lens whose radii of curvature are different is forming the image of an object placed on its axis. If the lens is placed with its faces reversed, will the position of the image change?

24.What happens to focal length of a convex lens, when it is immersed in water ?

25.How does the focal length of a convex lens change if monochromatic red light is used instead of violet light?

26.The radii of curvature of both the surfaces of a lens are equal. If one of the surfaces is made plane by grounding, how will the focal length and power change?

27.A glass prism is held in water. How is the angle of minimum deviation affected?

28.A ray of light is normally incident on one face of an equilateral prism.Trace the course of the ray through the prism and emerging from it.

29. What will be the colour of the sky in the absence of atmosphere?

30. Why do clouds appear white?

31. Why do sometimes we observe haloes (rings) round the sun or the moon?

32. Bees can see objects in the ultraviolet light while human beings cannot do so. Why?

33. A chicken wakes up early in the morning and goes to sleep by sunset. Why?
or
Why is a chicken not able to see in the dim light?

35. Why is the focal length of an objective in compound microscope little shorter than the focal length of the eyepiece?

36. You are provided with four lenses of focal length 1 cm, 3cm, 10cm and 100cm. Which two would you prefer for a microscope and which two for a telescope?

37. Can we increase the range of a telescope by increasing the diameter of its objective?

38. A telescope has been adjusted for the relaxed eye. You are asked to adjust it for the least distance of distinct vision, then how will you change the distance between the two lenses?

39. The distances of an object and its real image, measured from the focus of a concave mirror, are a and b respectively. Show that f2 = ab.

40.A ray of light goes from medium 1 to medium 2. velocities of light in the two media are c1 and c2 respectively. For an angle of incidence q in medium 1, the corresponding angle of refraction in medium 2 is q/2.
(i) Which of the two media is optically denser and why?
(ii) Establish the relationship between q, c1 and c2.

41.A beam of light converges at a point on the screen. A plane parallel glass plate is introduced in the path of this converging beam. How will the point of convergence be affected? Draw the relevant ray diagram.

42. A microscope is focused on a dot at the bottom of a beaker. Some oil is poured into the beaker to a height of y cm and it is found necessary to raise the microscope through a vertical distance of x cm to bring the dot again into focus. Express refractive index of oil in terms of x and y.

43. A ray of light while traveling from a denser to a rarer medium undergoes total reflection. Derive the expression for the critical angle in terms of the speed of light in the respective media.

44.Explain the twinkling of stars. Why do the planets not show twinkling effect?
.
45. Only the stars near the horizon twinkle while those overhead do not twinkle. Why?

46.Show that a convex lens produces an N times magnified image when the objet distances, from the lens, have magnitudes (f ± f / N). Here f is the magnitude of the focal length of the lens. Hence find the two values of object distance, for which a convex lens, of power 2.5D, will produce am image that is four times as large as the object?

47.Use the lens equation to deduce algebraically what you know otherwise from explicit ray diagrams. (a) An object placed within the focus of a convex lens produce a virtual and enlarged image. (b) A concave lens produces a virtual and diminished image independent of the location of the object.

48. A beam of white light on passing through a hollow prism gives no spectrum. Why?

49. Give reasons for the following observations on the surface of the moon: (i) Sunrise and sunset are abrupt. (ii) Sky appear dark. (iii) A rainbow is never formed.

50. The bottom of a container is a 4.0 cm thick glass. (m=1.5) slab. The container contains two immiscible liquids And B of depths 6.0 cm and 8.0 cm respectively. What is the apparent position of a scratch on the outer surface of the bottom of the glass slab when viewed through the container? Refractive indices of A and B are 1.4 and 1.3 respectively.

51. The refractive index of water is 4/3. Obtain the value of the semivertical angle of the cone within which the entire outside view would be confined for a fish under water. Draw an appropriate ray diagram.

52. A lens forms a real image of an object. The distance of the object to the lens is 4 cm and the distance of the image from the lens is v cm. The given graph shows the variation of v with u. (i) What is the nature of the lens? (ii) Using this graph, find the focal length of this lens.


53. A ray of light passes through an equilateral glass prism, such that the angle of incidence is equal to the angle of emergence. If the angle of emergence is ¾ times the angle of the prism, Calculate the refractive index of the glass prism.

54. State the conditions which must be satisfied for two light sources to be coherent.

55. Two independent light sources cannot act as coherent sources. Why?

56. No interference pattern is detected when two coherent sources are infinitely close to one another. Why?

57. If the path difference produced due to interference of light coming out of two slits for yellow colour of light at a point on the screen be 3l/2, what will be the colour of the fringe at the point. Give reason also.

58. What happens to the interference pattern if the phase difference between the two sources varies continuously?

59. Radiowaves diffract pronouncedly around the buildings, while light waves, which are e.m. waves do not why?

60. Coloured spectrum is seen, when we look through a muslin cloth. Why.

 

 

CBSE Physics (Chapter Wise With Hint / Solution) Class XII (By Mr. Sreekumaran Nair)