Ray Optics and Optical Instruments Mock Test – Class 12 Physics

1. An optical device is useful in ray optics when its action can be understood by following the change in direction of light rays. A suitable example is

2. Assertion: Ray optics cannot give a full explanation of diffraction fringes produced by a very narrow slit.
Reason: Ray optics treats light mainly as travelling along geometrical rays and does not include strong wave spreading at wavelength-sized openings.

3. A primary rainbow is formed mainly due to sunlight undergoing

4. The following standard lens rays are recorded:

The correct rows are

5. For two separated lenses, a virtual object for the second lens can occur when

6. An instrument has a short focal length objective, a short focal length eyepiece, and a tube length much larger than both focal lengths. It is most likely a

7. A plane mirror forms an image of a candle placed in front of it. The image is virtual mainly because

8. A concave mirror receives rays from a very distant object. The rays reaching the mirror may be treated as nearly parallel, so the image is formed approximately at

9. Consider the following statements about the ray model:
I. A ray shows the direction of propagation of light.
II. A ray can be regarded as normal to a wavefront in the basic wavefront picture.
III. Ray optics fully explains strong diffraction around very small obstacles.
The suitable choice is

10. A spherical refracting surface has , , , and . If the object height is , the image distance and image height are

11. The image formed by a convex mirror is always diminished for a real object because

12. The scattering intensity for Rayleigh scattering varies with wavelength as

13. Two plane mirrors are arranged at right angles, and a small object is placed symmetrically between them. The expected number of images is

14. The absolute refractive index has no unit because it is

15. A mirror calculation gives for a real object. This result is most consistent with

16. Two convex lenses and have focal lengths and , respectively. If both receive parallel rays from a distant object, the correct comparison is

17. A graph is drawn for two fixed convex lenses separated by distance , with on the vertical axis and on the horizontal axis. According to , the graph is

18. Ordinary image formation by a classroom lens is usually treated with ray optics because

19. Presbyopia commonly occurs with age because

20. An object is kept between two plane mirrors inclined at . If the object is on the angle bisector, the number of images is

21. A concave mirror has focal length . An object is placed in front of it. The image position is

22. A concave mirror forms a real image in front of it when an object is placed in front of the mirror. The focal length of the mirror is

23. A convex spherical glass surface has , , , and . If the image distance is , the lateral magnification is

24. A comparison table for optical instruments is given:

The acceptable rows are

25. Consider these statements about prism dispersion:
I. Dispersion occurs because refractive index depends on wavelength.
II. In ordinary glass, violet light is deviated more than red light.
III. Angular dispersion is the same as the mean deviation of yellow light.
IV. Dispersive power is a dimensionless ratio.
The suitable set is

26. A telescope has normal-adjustment magnifying power . Its eyepiece focal length is changed from to , while the objective focal length is unchanged. The new magnifying power is

27. Consider the following statements about refraction:
I. The angles in Snell's law are measured from the normal.
II. At a boundary, the frequency of a light wave remains unchanged.
III. If , an obliquely incident ray bends toward the normal in medium .
The suitable choice is

28. A concave mirror produces an inverted image that is larger than the object. The most suitable object position is

29. A ray from air enters a glass prism and later emerges back into air. The emergent ray is not parallel to the incident ray mainly because

30. For the telescope with , , and , the tube length for final image at the near point is

31. A glass lens is placed in a liquid having the same refractive index as the glass. The lens becomes ineffective for focusing because

32. A concave mirror of focal length forms a real image of a tall object with magnification . The object distance and image distance are respectively

33. Hypermetropia is a defect in which a person usually has difficulty seeing

34. Assertion: A rainbow is seen in the direction opposite to the Sun.
Reason: Rays from the Sun are refracted, internally reflected, and refracted again by raindrops before reaching the observer's eye.

35. A thin lens can be understood at first as

36. A spectacle lens marked is used as a thin lens. A real object is placed in front of it. The image distance is

37. A ray passes through a glass slab of thickness . The angle of incidence is , and the refractive index of glass is . If , the lateral displacement is approximately

38. A microscope and a telescope are both included in ray optics because their working can be started by studying

39. The power of a lens is defined as

40. The mirror formula for a spherical mirror under the paraxial approximation is

41. A converging lens of power is kept in contact with a diverging lens of power . A real object is placed in front of the combination. The image distance is

42. In a concave-lens ray diagram, the refracted rays from the top of a real object are diverging. The image point is located by

43. A student claims that a convex mirror can form a real image of a real object if the object is taken very far away. The claim is

44. A graph of Rayleigh scattering intensity against wavelength is described for visible light. As increases from blue toward red, should

45. A table of lens formula interpretations is shown below:

The acceptable rows are

46. Consider these statements about a concave lens:
I. It forms a virtual image for a real object.
II. Its image is erect for a real object.
III. Its image is magnified for every real-object position.
IV. Its image lies between and on the object side.
The suitable set is

47. Light is travelling from glass into air. A ray inside glass is incident at . The critical angle satisfies . The correct conclusion is

48. A Galilean telescope differs from the usual astronomical telescope because its eyepiece is

49. A prism has . At a certain setting, and . If the prism is turned to the minimum-deviation position and the least deviation is , the new angle of incidence is

50. A medical endoscope uses optical fibres to view internal organs. The relevant optical principle is