
Matching List-I (Optical Instruments) with List-II (Nature of Lens/Mirror Used):
| Optical Instrument | Nature of Lens/Mirror Used | Correct Match |
|---|---|---|
| (A) Human eye | (III) Lens of adjustable focal length | A → III |
| (B) Microscope | (IV) Objective of small aperture and small focal length | B → IV |
| (C) Reflecting telescope | (I) Concave mirror of large aperture and large focal length | C → I |
| (D) Refracting telescope | (II) Objective lens of large aperture and large focal length | D → II |
Final Matching:
Let's analyze each optical instrument and the nature of the lens/mirror it uses:
Therefore, the correct matching is:
A - III (Human eye - Lens of adjustable focal length)
B - IV (Microscope - Objective of small aperture and small focal length)
C - I (Reflecting telescope - Concave mirror of large aperture and large focal length)
D - II (Refracting telescope - Objective lens of large aperture and large focal length)
A slanted object AB is placed on one side of convex lens as shown in the diagram. The image is formed on the opposite side. Angle made by the image with principal axis is: 
Three friends, P, Q, and R, are solving a puzzle with statements:
(i) If P is a knight, Q is a knave.
(ii) If Q is a knight, R is a spy.
(iii) If R is a knight, P is a knave. Knights always tell the truth, knaves always lie, and spies sometimes tell the truth. If each friend is either a knight, knave, or spy, who is the knight?