Optics Question 343
Question: The focal length of objective and eye lens of a microscope are 4 cm and 8 cm respectively. If the least distance of distinct vision is 24 cm and object distance is 4.5 cm from the objective lens, then the magnifying power of the microscope will be
Options:
A) 18
B) 32
C) 64
D) 20
Show Answer
Answer:
Correct Answer: B
Solution:
For objective lens $ \frac{1}{f _{o}}=\frac{1}{v _{o}}-\frac{1}{u _{o}} $
$ \Rightarrow \frac{1}{(+4)}=\frac{1}{v _{o}}-\frac{1}{(-4.5)} $
$ \Rightarrow v _{o}=36\ cm $
$ \therefore |m _{D}|\ =\frac{v _{o}}{u _{o}}( 1+\frac{D}{f _{e}} )=\frac{36}{4.5}( 1+\frac{24}{8} )=32 $
