Exercise, 10th Sci. 1,  7. Lenses

                

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1. Write uses of simple microscope.

2. The apparent size of an object depends on the ... subtended by the object at the eye.

3. R = 5 * 20 / -20, FIND R = ? 

4. Define the farthest distance of distinct vision.

5. The ... of a lens depends on its focal length.

6. Define optical center (O).

7. If an object is placed in front of the convex lens at infinity, then write down the size of the image.

8. Write three rules to draw ray diagrams of images obtained by convex lenses.

9. Write names of different types of lenses.

10. Write the lens formula.

11. All distances parallel to the principal axis are measured from the ... .

12. There is a dark, fleshy screen behind the cornea. This is called the ... .

13. For a normal human eye, the far point is at ... .

14. The peephole in the door that helps us see a large area outside the door. This uses one or more ... lenses.

15. In a compound microscope the image formed by the first lens acts as the ... for the second lens.

16. In the human eye, the image remains imprinted on our retina for ... th of a second after the object is removed.

17. The image formed by a ... lens is always virtual, erect, and smaller than the object.

17.1 Draw an image for a concave lens.

18. The doctor has prescribed a lens having a power of +2.5 D. What will be the focal length of the lens? What is the type of the lens and what must be the defect of vision?

19. What is this distance between the lens and the screen called?

20. A ray of light gets refracted ... while passing through a lens.

21. If the position of the object is between F₁ and O in front of a convex lens, then write down the nature of the image.

22. Why is a convex lens called a converging lens?

23. In a concave lens, if the check is anywhere between the optical center and infinity, then what is the size of the image? 

24. Write the Cartesian sign convention.

25. If the size of the image is the same size and the position of the image is at 2 F2 then what is the position of the object in front of a convex lens?

26. The unit of the power of a lens is ... .

27. Draw and label the human eye. 

28. 1/v = 1/-20 + 1/10. Find v.

29. ... lens is used to spread widely the light produced by a small bulb inside

a torch.

30. In bifocal lenses, the upper part is a concave lens and corrects ... .

31. Write the names of two types of telescopes. 

32. Which are the two light-sensitive cells?

33. The spectacles used to correct farsightedness have ... power.

34. A ... is a transparent medium bound by two surfaces. 

35. Define radius of curvature (R).

36. When an object is placed between F₁ and 2F₁ in front of a convex lens and the size of the image is large, then write down the position of the image.

37. Distances perpendicular to the principal axis and above it are taken to be ... .

38. If two lenses with focal lengths f1 and f2 are kept in contact with each other, then write the formula for the combination of lenses.

39. The focal length of a convex lens is 25 cm. What is its power?

40. Define power of accommodation.

41. There is a very thin transparent cover (membrane) on the human eye. This is called ... .

42. Write the formula for magnification.

43. What is mean by the near point of the eye?

44. Write the difference between nearsightedness and farsightedness.

45. In bifocal lenses, the lower part is a convex lens, which corrects the ... .

44.1. Define nearsightedness.

44.2. Where is the image formed in the nearsightedness defect?

44.3. What are two reasons for the nearsightedness defect?

44.4. How can the nearsightedness defect be corrected?

44.1. 1. Define farsightedness.

44.2.1. Where is the image formed in the farsightedness defect?

44.3.1. What are two reasons for the farsightedness defect?

44.4.1. How can the farsightedness defect be corrected?

46. A lens with ... power is required for correcting nearsightedness.

47. Define persistence of vision.

48. A convex lens is called a simple microscope or ... lens.

49. The focal length of a ... lens is positive.

50. Write two rules for the images obtained by concave lenses.

51. Define focal length (f).

52. Write uses of lenses in day-to-day life.

53. In a convex lens, if the position of the image is at infinity in a convex lens, then what is the position of the object?

54. Power is the inverse of its focal length (f); f is expressed in ... .

55. There is a small hole of changing diameter at the centre of the iris, which is called

the.... .

56. Write the formula for the power of a lens.

57. Write 4 uses of concave lenses.

58. One can get a ... times larger image of an object using simple microscopes.

59. Conical cells do not respond in .... .

60. Which are three types of refraction defects?

61. The eyeball is approximately spherical and has a diameter of about ... cm.

62. The lens with both surfaces spherical on the inside is called a ... lens.

63. Rays travelling parallel to the principal axis of a concave lens ... after refraction in such a way that they appear to be coming out of a point on the principal axis.

64. In a relaxed state, the focal length of healthy eyes is ... cm.

65. Why does the direction of the ray change while emerging from the lens?

66. For a normal human eye, the near point is at ... cm.

67. Define principal axis.

68. Explain the term "color blind."

69. Write the difference between a concave lens and a convex lens.

70. In a convex lens, if the position of the object is beyond 2F₁ and the position of the image is between F₂ and 2F2, then write down the size of the image.

71. Define center of curvature (C).

72. In a concave lens, if the object is at infinity, then what is the size of the image? 

73. The ...-like cells respond to the intensity of light and give information about the brightness or dimness of the object to the brain.

74. The ... cells respond to the colour and give information about the colour of the object to the brain.

75. Define Principal focus (F)

76. Define the power of a lens.

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