21. Total internal reflection is the basic principle behind working of __________.

22. An optical fiber is very thin fiber made of ____________ having radius about a micrometer.

23. One Micrometer is equeal to ______ m.

24. A bunch of optical thin fibers form a __________.

25. When light is entered into optical fiber, the angle of incidence is greater than the critical angle and hence ______________ takes place.

26. The distance between the parallel rays in a glass slab is called ____________.

27. The refractive index of a glass slab is calculated by using the formula, = ___________

28. When the angle of incidence is greater than the critical angle, the light ray is reflected into denser medium at interface. This phenomenon is called __________________.

29. The refractive index of air is ___________

30. The refractive index of Ice is __________

31. The refractive index of Rock salt is _________

32. The refractive index of Water is _______

33. The refractive index of Kerosene is _________

34. The refractive index of Turpentine oil is ________

35. The refractive index of Crown glass is ________

36. The refractive index of Diamond is ______

37. At critical angle of incidence, the angle of refraction is

38. n1 sin i = n2 sin r, is called __________.

39. Speed of light in vaccum is ________ m/s.

40. Total internal reflection takes place when a light ray propagates from ________ to _________ medium.

41. The refractive index of a transparent material is 3/2. The speed of the light in that medium is __________ m/s.