Ray Optics and Optical Instruments Mock Test – Class 12 Physics

1. If the two media on the two sides of a spherical surface have the same refractive index, the surface produces no refraction in the ideal model because

2. A student writes, “Total internal reflection happens because the refracted ray bends toward the normal until it becomes impossible.” The needed correction is that the refracted ray

3. A real object is placed before an optical element. The image is real, inverted, and diminished. This image can be formed by

4. A prism has angle and refractive index . At minimum deviation, the value of is

5. A simple microscope, a compound microscope, and an astronomical telescope all use lenses, but the object for a telescope is usually

6. The image formed on the retina of a normal eye is

7. For a normal human eye, the least distance of distinct vision is usually taken as

8. A learner says, “A concave lens can give a real inverted image if the object is kept far enough.” The best correction is that a concave lens in air

9. The dispersive power of a prism material is commonly expressed as

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

11. A microscope is required to distinguish two very close points in a specimen. The resolution is improved by using

12. Assertion: Interchanging and in the spherical refracting surface formula generally changes the result.
Reason: and represent the incident and refracted media, so their placement carries the direction of light crossing the surface.

13. A dentist uses a concave mirror of focal length to see an enlarged erect image of a tooth. If the tooth is in front of the mirror, the image distance and magnification are

14. In normal adjustment of an astronomical telescope, the distance between the objective and eyepiece is approximately

15. A concave spherical mirror is used with a narrow beam of rays parallel to its principal axis. After reflection, the rays meet near the

16. 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

17. A prism of angle is adjusted to minimum deviation. If the minimum deviation is , the angle of incidence is

18. A light ray passes from water into air and reaches an observer’s eye. The observer traces the ray backward in a straight line to locate an apparent image. This use of backward tracing is justified mainly by

19. A convex lens and a rectangular glass slab are both made of glass, but only the convex lens can focus parallel rays in air. The main reason is that

20. A comparison of optical media is shown below:

The comparison is

21. When a light ray passes obliquely from air into glass, it bends toward the normal mainly because

22. The angular dispersion produced by a prism for violet and red light is

23. A ray passes through the optical centre of a thin lens. In the usual thin-lens ray diagram, the ray is drawn

24. A beam containing red and blue light travels through a long atmospheric path near sunset. The direct light reaching an observer is richer in red because

25. A convex lens of focal length and a concave lens of focal length are separated by . The equivalent focal length is

26. Use the lens arrangement described here: a thin concave lens receives a ray parallel to its principal axis from the left. After refraction, the ray

27. An astronomical telescope has , , and . The difference between magnifying power at near-point adjustment and normal adjustment is

28. For a convex lens to act as a simple microscope, the object should be placed

29. A small object in air is placed in front of a convex spherical glass surface of radius . For light travelling from air into glass , the image distance is

30. For a thin prism of small angle , the approximate deviation produced for monochromatic light is

31. A learner writes for a concave mirror whose reflecting surface faces the incoming light. The most precise correction is

32. The eyepiece of a compound microscope mainly acts as

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

34. Chromatic aberration is absent in a reflecting telescope objective because

35. A thin lens can be understood at first as

36. The eyepiece of an astronomical telescope mainly

37. A simple microscope increases apparent size mainly by increasing

38. A small object is slowly moved toward the focus of a concave mirror from a position between and . The real image moves

39. A student says, “A magnifying glass should have a long focal length to give large magnification because long lenses are bigger.” The best correction is that

40. A thin prism gives mean deviation and angular dispersion . Its dispersive power is

41. A ray crosses from medium to medium without any change in direction even though it meets the boundary obliquely. The best conclusion is that

42. In refraction at a spherical surface, the formula uses for the medium in which

43. In an astronomical telescope, the objective forms the first image of a distant object approximately

44. A hypermetropic person's near point is . The spectacle lens should allow reading at . The required power is

45. Two thin lenses of focal lengths and are separated by . The equivalent focal length of the system is

46. A telescope is mainly used to view

47. A graph of lateral displacement against slab thickness is drawn for a fixed material and fixed angle of incidence. The graph is expected to be

48. The principal axis of a spherical mirror is the straight line passing through

49. A learner mixes up microscope and telescope formulas. The expression belongs to

50. For a real object placed anywhere in front of a concave lens in air, the image is formed