Assignment X Light Reflection of Light: Reflection and refraction of light. 1. What is light and define the duality of light? 2. Write five characteristics of light. 3. Explain the following terms (a) Angle of incidence (b) Angle of reflection (c) principle axis (d) pole (e) Aperture (f) center of curvature (g) object (h) image 4. Write the law of reflection. 5. Define the term lateral inversion. 6. Write the properties of image formed by the plane mirror? 7. Define the principle focus of concave mirror? 8. Define the principle focus of convex mirror? 9. Explain the following term (a) focal length (b) radius of curvature (c) object distance (d) image distance (e) real image (f) virtual image 8. What is the relation between the focal length and radius of curvature? 9. What is the relation between the focal length, image distance and object distance? 10. Write the sign convention of coordinate system. 11. Write the rule for forming image in concave mirror? 12. Write the rule for forming image in convex mirror? 13. Define the term linear magnification. 14. The magnification produced by a plane mirror is + 1. What does this mean?
15. What are your observations when you try to see the image of a large size distant object (say a distant tree) formed by a (i) concave mirror, (ii) plane mirror, and (iii) convex mirror? 16. We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. what should be the range of distance of the object from the mirror? What is the nature of the image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case. 17. An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image. 18. An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. find the position of the image, its nature and size. 19. An object of size 7.0 cm is, placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image. 20. A ray of light is passing through the centre of curvature of a concave mirror. What will be the direction of reflected ray? 21. From the mirror equation show that the image in a plane mirror is as far behind the mirror as the object is in front of it. 22. What happens when the rays of sun are focused at a point on the paper by using concave mirror? 23. Define principal focus of a convex spherical mirror. Draw a diagram too. 24. Show geometrically that for a spherical mirror R = 2f. 25. Draw a neat diagram to show image formation by a convex mirror for an extended object placed in front of it. State the characteristics of the image. 26. An object is placed at a distance of 12 cm in front of a concave mirror. It forms a real image 4 times larger than the object. Calculate the distance of the image from the mirror 27. An object of 5 cm is placed at a distance of 25 cm from the pole of a concave mirror of radius of curvature 30 cm. Calculate the distance and size of the image so formed. What will be the nature of the image? 28. A convex mirror used for rear view on an automobile has radius of curvature of 3.00 m. If a bus is located at 5.0 m from the mirror, find the position, nature and size of the image. 2
29. An object 2.0 cm high is placed 20.0 cm in front of a concave mirror of focal length 10.0 cm. Find the distance fro the mirror at which a screen should be placed in order to obtain a sharp image. What will be the size and nature of the image formed? 30. An object 2 cm in size is placed 30 cm in front of a concave mirror of focal length 15 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image? What will be the nature and the size of the image formed? Draw a ray diagram to show the formation of the image in this case. 31. Draw ray diagrams to show the formation of images when the object is placed in front of a concave mirror: (i) between its pole and focus point. (ii) Between its center of curvature and focus point. 32. An object 4.0 cm in size, is placed 25.0 cm in front of a concave mirror of foal length 15.0 cm. at what distance from the mirror should a screen be placed in order to obtain a sharp image? Find the nature and the size of the image. Refraction of Light: 1. What is refraction of light? 2. State law of refraction? 3. Define refractive index? (i) Absolute refractive index (ii) Relative refractive index 4. State the Snell s law? 5. Explain the following term (a) Angle of refraction (b) Angle of deviation (c) Angle of emergence 6. Define the principle focus of convex lens and draw its diagram? 7. Define the principle focus of concave lens and draw its diagram? 8. Write the rule for forming image in convex lens? 9. Write the rule for forming image in concave lens? 10. Explain the sign convention for the spherical lens? 11. What is lens formula? 12. What is linear magnification of spherical lens? 13. Write the relation between magnification and focal length of spherical lens? 14. How the magnification is related to the image distance and object distance? 3
15. Define power of lens? 16. Define one diopter? 17. What is the SI unit of refractive index? 18. What is the possible value of absolute refractive index of a medium? 19. How is the refractive index of an optical medium related to the speed of light in that medium? 20. Refractive index of water with respect to air is 1.33. What is the refractive index of air with respect to water? 21. How does refractive index of one medium with respect to another depend on their absolute refractive indices. 22. In which medium light travels faster, in a denser medium or in a rarer medium? 23. If a light ray IM is incident on the surface AB as shown, identify the correct emergent ray. 24. For the same angle of incidence of 45, the refraction angle in two transparent media P and Q is 20 and 30, respectively. Which medium is optically denser out of P and Q and why? 25. What is lateral displacement of a light ray passing through a glass slab? 26. Prove that the angle of incidence is equal to the angle of emergence when a ray of light passes through a glass slab. 27. A light ray is incident normally on a glass slab. What will be the value of lateral displacement? 28. The refractive indices of four media A, B, C and D are given in the following table: Medium A B C D Refractive index 1.33 1.50 1.52 2.40 29. If light travels from one medium to another, in which case the change in speed will be (i) minimum, (ii) maximum? 30. A virtual image is formed by a convex lens. Where is the object placed? 31. An image of the same size of an object is formed in a convex lens. Where is the object situated and where is the image formed? 32. An object is placed at the focus of a concave lens, where will the image be formed? 33. One half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? verify your answer experimentally. Explain your observations. 34. An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed. 4
35. A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram. 36. What is the difference between virtual image of an object formed by a convex lens and that formed by a concave lens? 37. Light enters from air into water which has a refractive index of 1.33. Calculate the speed of light in water. The speed of light in air is 3.0 10⁸ m/s. 38. If the refractive index of a medium is 2 what does its means? 39. What is the relation between the refractive index and the speed of light in that medium? 40. If the refractive index of glass w.r.t water is 1.17 then find the refractive index of water w.r.t glass. 41. If n 21 and n 31 be the refractive indices of medium numbers 2 and 3, respectively with respect to media number 1, then what is the value of refractive index of media number 3 with respect to media number 2? 42. With respect to air the refractive indices of water and benzene are 1.33 and 1.50 respectively. Calculate the refractive index of benzene with respect to water. 43. With respect to air the refractive index of kerosene is 1.44 and that for diamond is 2.42. calculate the refractive index of diamond with respect to kerosene. 44. Draw ray diagrams to show image formed by a concave lens for the object placed (a) at infinity, (b) between infinity and optical centre of lens. State characteristics of image in each case. 45. We wish to obtain a real, inverted image of the same size as that of the object by a thin convex ens of focal length 20cm. Where should the object be placed? Draw the ray diagram to show the image formation. 46. Draw a labelled ray diagram to locate the image of a object formed by a convex lens of focal length 20 cm when the object is placed 30 cm away from the lens. 47. An object 5.0 cm tall is placed on principal axis of a convex lens. Its 2.0 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens. 48. Draw a ray diagram to show refraction through a rectangular glass slab. How is the emergent ray related to indecent ray? What is its lateral displacement? 49. For refraction through a glass slab show that angle of emergence is equal to the angle of incidence. 50. A 2.0 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 10 cm. the distance of the object fro the lens is 15 cm. find the nature, position and size of the image. Also find its magnification. 5
51. A 5 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. find the (i) position, (ii) nature, and (iii) size of the image formed. 52. An object 3 cm high is placed at a distance of 24 cm in front of a convex lens of focal length 16 cm. find the position, nature and size of the image formed. 53. A convex lens has a focal length of 10 cm. At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm away from the lens? What would be the size of the image formed if the object is 2 cm high? With the help of a ray diagram show the formation of the image by the lens in this case. 54. A 10 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 30 cm. The distance of the object fro the lens is 20 cm. Find the (i) position, (ii) nature, and (iii) size of the image formed. 55. A convex lens has a focal length of 25 cm. calculate the distance of the object from the lens if the image is to be formed on the opposite side of the lens at a distance of 75 cm from the lens. What will be the nature of the image? 56. A concave lens has focal length of 20 cm. At what distance from the lens a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed. 57. An object 3.0 cm high is placed perpendicular to the principal axis of a concave lens of focal length 15.0 cm. The image is formed at a distance of 10.0 cm from the lens. Calculate (i) distance at which the object is placed, and (ii) size and nature of the image formed. 58. What do you mean by power of a lens? How does it depend upon the focal length? What it the meaning of positive and negative powers? 59. A 2 cm high candle flame is placed at a distance of 80 cm from a white screen. On placing a convex lens exactly at the mid point of the candle and the screen. A distinct image of the flame is seen on the screen. What is the focal length of the lens and the size of the candle flame image formed? Draw a ray diagram to show the formation of the image in this case. 60. What is the power of plan mirror? 61. The power of a lens is 4.0 D. What is the nature of the lens? 62. What is the power of a diverging lens of focal length 20 cm? 63. What is the power of Converging lens of focal length 20 cm? 6
64. Find the focal length of a lens of power 2.0 D. What type of lens is this? 65. Two thin lenses of powers P₁ and P₂ are placed in contact. What is the power of the combination? 66. A doctor has prescribed a corrective lens of power + 1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging? 67. A convex lens of focal length + 30 cm is combined with a concave lens of focal length 30 cm. what is the power of the combined lens? 68. Two lenses of power + 3.5 D and 1.5 D are placed in contact. What is the power and focal length of the combination? If an object be placed at a distance of 0.8 m from the lens combination, where is the image formed? 7