Physics XI Karachi Board True and False - Chapter 10

Chapter 10 - Geometrical Optics
1. A lens is a piece of opaque material that can focus a transmitted beam of light.

2. A lens is a piece of transparent material that can focus transmitted light.

3. A lens is a piece of transparent material that can focus reflected beam of light.

4. A lens is usually bounded by two spherical surfaces.

5. A lens is usually bounded by two plane surfaces.

6. A lens is usually bounded by the spherical and plane surfaces.

7. Lenses fall into two categories.

8. A convex lens is thicker in the middle and thinner on the edges.

9. A convex lens is thinner in the middle and thicker on the edges.

10. A convex lens converges the light rays towards its optical axis.

11. A convex lens diverges the light rays away from the optical axis.

12. A concave lens is thinner in the middle and thicker on the edges.

13. A diverging lens is thicker in the middle and thinner on the edges.

14. A concave lens bends the light rays from its optical axis.

15. A diverging lens converges the light rays from its optical axis.

16. The point to which the light rays are brought to focus is called Principal Focus.

17. The point to which the light rays are brought to focus is called optical axis.

18. Optical centre of the lens is the point in it whrough which the light rays will pass without any deviation.

19. In converging lens when the object is placed at 2F then its image will form beyond 2F on the other side of the lens.

20. The focal length of the converging lens is taken as positive.


21. The reciprocal of the focal length of equivalent lens is equal to the sum of the reciprocals of the focal lengths of the two lenses.

22. The power of the equivalent lens is equal to the sum of the power of the two lenses.

23. The defect in the lens due to the fact that different wave lengths of the light refracted by lens focus at different points is called chromatic aberration.

24. The lens defect call spherical aberration can by minimized by using the central part of the lens.

25. Magnification of the lens is defined as the ratio of the size of the object to the size of the image.

26. The apparent size of an object does not depend upon the visual angle.

27. The least distance of distinct vision for a normal person is 25cm.

28. Compound microscope consists of three lenses.

29. In compound microscope the focal length of the objective is less than the focal length of eye-piece.

30. Compound microscope gives the higher magnification than that of magnifying glass.

31. Astronomical Telescope consists of two diverging lenses.

32. The magnifying power of the astronomical telescope is the ratio of focal length of eye-piece to the focal length of the objective.

33. In Galilean telescope the concave lens will be used as an eye piece.

34. In terrestrial telescope third lens is called erecting lens.

35. In spectrometer collimeter is fixed to the base of the instruments.

36. The spectrum of the light, which consists of a series of bright lines is called Line Spectrum.

37. In eye the iris is a muscular diaphragm that controls the size of the pupil.

38. When the eye produces an image of distant object behind retina, the abnormality is known as Myopia.

39. In the abnormality named as Hyperopia the person is said to be far sighted.

40. Far sightedness can be corrected by using the convex lens.