1st Year Physics Chapter 10 Optical Instruments Notes MCQs Bank

physics 11th notes Chapter 10

1. Typical fibre optic communication system uses the light of which wavelength?

 
 
 
 

2. Light signals passes through multimode graded fiber due to:

 
 
 
 

3. Refractive index is given by:

 
 
 
 

4. Michelson devised the formula to calculate speed of light?

 
 
 
 

5. The central image in a compound microscope is:

 
 
 
 

6. For normal adjustment, length of astronomical telescope is:

 
 
 
 

7. Critical angle is that incident angle in denser medium for which angle of refraction is.

 
 
 
 

8. A spectrometer is used to find?

 
 
 
 

9. Large astronomical telescopes are of which type?

 
 
 
 

10. The magnifying power of an astronomical telescope is:

 
 
 
 

11. Who invented photophone?

 
 
 
 

12. If the red light is replaced by blue light illuminating the object in a microscope the resolving power of the microscope?

 
 
 
 

13. The value of critical angle for glass-air boundary is:

 
 
 
 

14. If a single convex lens is placed close to the eye, it can be used as a

 
 
 
 

15. The diamond shines due to:

 
 
 
 

16. For the phenomenon of total internal reflection, the angle of incidence should be:

 
 
 
 

17. A lens which converges a beam of parallel rays to a point is called:

 
 
 
 

18. The least distance of distict vision for a normal eye is:

 
 
 
 

19. The magnifying power of a simple microscope is:

 
 
 
 

20. A point where the incident parallel rays of light converge or appear to diverge after passing through a lens is called

 
 
 
 

21. The speed of light in the medium of the refractive index of 1.5 is?

 
 
 
 

22. In going from a denser to rare medium a ray of light is?

 
 
 
 

23. Least distance of distinct vision of normal and healthy people:

 
 
 
 

24. A real object placed inside the focus of a convex lens gives:

 
 
 
 

25. Magnification of the astronomical telescope is?

 
 
 
 

26. Which color has the maximum angle of deviation in prism?

 
 
 
 

27. At some angle of incidence, when angle of refraction becomes 90°, this angle is called:

 
 
 
 

28. A convex length of focal length ‘f1’ and concave lens of focal length ‘f2’ are placed in contact. The focal length of the combination is:

 
 
 
 

29. Critical angle is that incident angle in denser medium for which angle of refraction is.

 
 
 
 

30. Final image produced by a compound microscope with respect to the object is?

 
 
 
 

31. Image of an object 5 mm high is only 1 cm high. Magnification produced by a lens is:

 
 
 
 

32. The electrical signals change into light signals for transmission through optical fiber. A light pulse represents.

 
 
 
 

33. Michelson calculated the speed of light using the instrument?

 
 
 
 

34. If a convex lens of focal length ‘f’ is cut into two identical halves along the lens diameter, the focal length of each half is?

 
 
 
 

35. In Michelson’s experiment, the equation used to find te speed of light is:

 
 
 
 

36. In optic fiber transmission system __________ are used to regenerate the dim light signal.

 
 
 
 

37. A surfboard moves at an aped of 5ms⁻¹on the crests of the wave. The distance between wave crests is 10m. What is the frequency of the wave motion?

 
 
 
 

38. A convex and concave lens of focal length ‘f’ are in contact. The focal length of the combination will be?

 
 
 
 

39. Dispersion effect may produce an error in light signals. This type of error is minimum in:

 
 
 
 

40. In a convex lens of large aperture fails to converge the light rays incident on it to a single point, it is said to suffer from?

 
 
 
 

41. Which of the phenomenon of light is used in propagation of light through optical fibers?

 
 
 
 

42. The electrical signals change into light signals for transmission through optical fibre. A light pulse represents.

 
 
 
 

43. In going form a denser to rarer medium an array of light is

 
 
 
 

44. In multimode step index fiber the refractive index of core and cladding is

 
 
 
 

45. Dispersion effect may produce error in light signals. This type of error is minimum in:

 
 
 
 

46. The function of collimator in spectrometer is?

 
 
 
 

47. The equation αmin = 1.22 λ/D was devised by?

 
 
 
 

48. If the length of the telescope is 96cm the focal lengths of its lenses is:

 
 
 
 

49. In optic fibre transmission, the repeaters are separated through a distance of _________ km in newer system.

 
 
 
 

50. A lens, which is thicker at the center and thinner at the edges, is called?

 
 
 
 

51. Which one type of fibre is more suitable for transmission of signals in which white light is used?

 
 
 
 

52. A point where the incident parallel rays of light converge or appear to diverge after passing through a lens is called?

 
 
 
 

53. If an object is placed away from ‘2f’ of a converging lens, then the image will be?

 
 
 
 

54. The minimum distance between an object and its real image in a convex lens is:

 
 
 
 

55. There is a noticeable boundary between core and cladding for?

 
 
 
 

56. If a lens is covered with wax then?

 
 
 
 

57. The optical fiber in which the central core has higher refractive index and its density gradually decreases towards its periphery is called:

 
 
 
 

58. Two convex lenses of equal focal length ‘f’ are placed in contact, the resultant focal length of the combination is:

 
 
 
 

59. Light signals pass through multimode graded-index fiber due to?

 
 
 
 

60. The magnifying power of a compound microscope is given by

 
 
 
 

61. The power of the lens is measured in:

 
 
 
 

62. The instrument which is used to measure speed of light was developed by

 
 
 
 

Short Questions

1. An astronomical telescope of having magnifying power of 5 consist two thin lens 24 cm apart. Find the focal lengths of the lens?
2. An octagonal mirror is rotating with frequency f. calculate the time of relation of one its sides?
3. Define critical angle and its formula?
4. Define least distance of distinct vision?
5. Define magnification 
6. Define magnifying power?
7. Define power of a lens and its unit?
8. Define refractive index?
9. Define resolving power?
10. Define total internal reflection and continuous refraction.
11. Define total internal reflection. 
12. Describe multimodi graded index fibre?
13. Describe with the help of diagramed, how a single biconvex lens can be used as a magnifying glass biconvex lenses can be arranged to from a microscope (compound)?
14. Differentiate between microscope and telescope. 
15. Distinguish between convex lens and concave lens?
16. Explain resolving power of an optical instrument?
17. Explain the difference between (a) signal mode (b) Multimode step index fibre?
18. Explain the difference between the angular magnification and resolving power of an optical instrument. What limits the magnification of an optical instrument?
19. Find the magnifying power of a convex lens of 25 cm. focal length?
20. How can a real image be be distinguished from a virtual image? Can each type of image be projected on a screen? Explain
21. How Convex Lens acts as magnifying glass?
22. How power is lost in optical fibr through dispersion?
23. How signal is transmitted and converted into sound in an optical fibres?
24. How the light signal is transmitted through the optical fiber?
25. How the power is last in optical fiber through dispersion? Explain.
26. How the power is last in optical fibre through scattering and absorption.
27. If a person were looking through a telescope at the full moon, how would the appearance of the moon be changed by covering half of the objective lens?
28. Name the instrument which is used to find the refractive index of transparent material?
29. One can buy a cheap microscope for use by the children. The images seen in such a microscope have colored images. Why is it so?
30. Show why a pinhole placed in front of a lens leads to good image even if the image is not quite in focus?
31. Under what conditions does a double convex lens acts as a diverging lens?
32. What are different type of optical fiber?
33. What are the conditions necessary for total internal reflection?
34. What are the problems having a high magnifying power in astronomical telescope?
35. What do you understand by linear magnification and angular magnification? Explain how a convex lens is used as a magnifier ?
36. What do you understand by Linear Magnification?
37. What is an optical fibre?
38. What is angular magnification?
39. What is collimator?
40. What is compound microscope?
41. What is difference between (i) chromatic aberration and (ii) spherical aberration?
42. What is simple microscope?
43. What is Snell’s law?
44. What is spectrometer?
45. what is the effect on the image if half of a converging lens is covered?
46. What is the function of collimator in a spectrometer?
47. What is the near point? Give its numerical value.
48. What is the spectrometer? Write the names of its essential components.
49. What is the total magnification produced by the microscope?
50. When light enters glass from air, its speed becomes less. Is it due to change in its frequency or wavelength?
51. When object lies within the principle focus of convex lens .what is the nature of image and where it is formed.
52. Why an objective of large aperture is used in a reflecting mirror telescope?
53. Why are danger signals in red when the eye is more sensitive to yellow and green?
54. Why do astronomers prefer reflecting telescope over refracting telescope?
55. Why do we use photodiode to transmit TV signal through optical fibre?
56. Why does a diamond sparkle more than a glass imitation of the a same shape and size?
57. Why is a beam of white light not dispersed into component colors when it passes perpendicularly through a pane of glass?
58. Why is a Convex Lens of small focal length preferred for a magnifying glass?
59. Why object of short focal length is preferred in microscope?
60. Why we use infrared light in a fiber optics communication
61. Why would it be advantageous to use blue light which a compound microscope?
62. Why would it be advantageous to use blue light with a compound microscope?
63. Write any two uses of spectrometer.
64. Write different types of optical fibres?
65. Write down the three major components on which fiber optic system consists.

Long Questions

1. Define resolving power of an instrument. Give its mathematical expression.
2. Define and explain Simple Microscope.
3. Define Compound microscope. Describe its construction, working and find its magnifying power.
4. What is an Astronomical telescope? Find its magnifying power.
5. Explain Michelson‟s method for measurement of speed of light.
6. What is spectrometer? Explain its all parts.
7. A converging lens of focal length 5 cm is used as a magnifying glass. If the neat point of the observer is 25cm and the lens is held close to the eye. Calculate (i) the distance of the object from the lens. (ii) the angular magnification. What is the angular magnification when the final image is formed at infinity?
8. A telescope objective has focal length 96cm and diameter 12cm. Calculate the focal length and minimum diameter of a simple eye piece lens for use with the telescope, if the linear magnification required is 24 times and all the light transmitted by the objective from a distant point on the telescope axis is to fall on the eye piece.
9. A telescope is made up of an objective of focal length 20cm and an eye piece of 5cm, both are convex lenses. Find the angular magnification.
10. A simple astronomical telescope in normal adjustment has an objective of focal length 100cm and an eye piece of focal length 5cm. (i) Where is the final image formed? (ii) Calculate the angular magnification.
11. A point object is placed on the axis of 3.6cm from a thin convex lens of focal length 3cm. A second thin convex lens of focal length 16cm is placed coaxial with the first and 26cm from it on the side away from the object. Find the position of the final image produced …
12. A compound microscope has lenses of focal length 1cm and 3cm. An object is placed 1.2cm from the object lens. If a virtual image is formed, 25 cm from the eye, calculate the separation of the lenses and the magnification of the instrument.
13. Sodium light of wavelength 589nm is used to view an object under a microscope. If the aperture of the objective is 0.9cm, (i) find the limiting angle of resolution, (ii) using visible light of any wavelength, what is the maximum limit of resolution for this microscope.
14. An astronomical telescope having magnifying power of 5 consist of two thin lenses 24cm apart. Find the focal lengths of the lenses.
15. A glass light pipe in air will totally internally reflect a light ray if its angle of incidence is at least 39 degree. What is the minimum angle for total internal reflection if pipe is in water? (Refractive index of water = 1.33)
16. The refractive index of the core and cladding of an optical fiber are 1.6 and 1.4 respectively. Calculate (i) the critical angle for the interface (ii) the maximum angle of incidence in the air, of a ray, which enters the fiber and is incident at the critical angle on the interface.

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