A microscope designer must build an instrument that provides an overall magnifying…
PHYSICS · Subjective · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
A microscope designer must build an instrument that provides an overall magnifying power of at least 600 while using an eyepiece of focal length not less than 4cm. The tube length available is fixed at 18cm.
(a) Show that with the given constraints a simple microscope cannot meet the required magnification.
(b) Prove that a compound microscope can satisfy the specification provided that the objective focal length obeys an appropriate inequality. Derive this inequality.
(c) Calculate the maximum permissible value of the objective focal length so that the design target is achieved.
(d) Suggest two practical difficulties that may arise if the objective focal length is chosen much smaller than the value obtained in part (c).