A hand-held magnifying glass consists of a single thin convex lens of focal length
PHYSICS · Multi-part · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
A hand-held magnifying glass consists of a single thin convex lens of focal length f=12cm. A user with a near point of 25cm wishes to view a small insect such that the image appears clearly at the near point and is upright.
(a) Derive an algebraic expression for the object distance s0 in terms of the focal length f and the near-point distance N that satisfies the viewing condition described above.
(b) Using your expression from part (a), calculate the minimum object distance s0 required for this user.
(c) Determine the angular magnification (also called the magnifying power) achieved under these conditions.
(d) Explain qualitatively how both the required object distance and the achievable magnification would change if the user’s near point were farther away (e.g., 40cm) while the lens focal length remained the same.