A student uses a single converging lens of focal length as a simple magnifier to read…
PHYSICS · Multi-part · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
A student uses a single converging lens of focal length f as a simple magnifier to read very small lettering.
(i) Derive an expression for the angular magnification when the final image is formed at infinity.
(ii) Derive a separate expression for the angular magnification when the final image is formed at the near point of the eye.
(iii) Using your results, show algebraically that the magnification in part (ii) is greater than that in part (i).
(iv) For f=4.0cm, calculate the numerical values of the magnifications obtained in both cases, taking the least distance of distinct vision as 25cm.
(v) Despite the higher magnification obtained in part (ii), explain quantitatively why the arrangement in part (i) is often recommended for prolonged use.