(i) Draw a neat, labelled ray diagram to show the formation of a virtual image by a…
PHYSICS · Subjective · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
(i) Draw a neat, labelled ray diagram to show the formation of a virtual image by a single converging lens when it is used as a reading magnifier with the final image situated at the least distance of distinct vision, D.
(ii) Starting from suitable expressions for the angular sizes of the object with and without the lens, derive an expression for the angular magnification of the magnifier in terms of D and the focal length f of the lens.
(iii) Keeping D fixed, explain qualitatively how the magnifying power varies with the focal length of the lens.
(iv) Give one reason why a lens of extremely small focal length is not generally preferred for ordinary reading even though it offers higher magnification.