A field biologist compares two hand lenses for outdoor observations.
PHYSICS · Multi-part · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
A field biologist compares two hand lenses for outdoor observations.
(i) Lens A has focal length 4cm, and Lens B has focal length 2.5cm. For a normal eye (D=25cm) viewing with the eye relaxed, calculate the magnifying power provided by each lens.
(ii) Determine the ratio of the magnifying power of Lens B to that of Lens A.
(iii) Lens B costs twice as much as Lens A. On the basis of magnifying power per unit cost, decide which lens is economically preferable. Justify your answer and mention one practical drawback that may arise when using a lens of very small focal length in the field.