Q7 of 52 Page 432

The separation between the objective and the eyepiece of a compound microscope can be adjusted between 98 cm to 118 cm. If the focal lengths of the objective and the eyepiece are 10 cm and 6 cm respectively, find the range of the magnifying power if the image is always needed at 24 cm from the eye.

Given data-


Focal length of the objective,


Focal length of the eyepiece,


Image distance from the eyepiece,


Distance between the objective and the eyepiece = 9.8 cm to 11.8 cm


Using lens formula


For eyepiece-




cm


1. When the separation between the objective and the eyepiece = 9.8 cm


for the objective lens, the image will be at a distance





Using lens formula for the objective lens –






Magnifying power of the compound microscope can be calculated as -




When the separation between the objective and the eyepiece is 11.8 cm





Using lens formula for the objective lens –






Magnifying power of the compound microscope can be calculated as -




Hence the magnification lies in the range of 20-30


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