Optics Question 335
Question: The focal lengths of the objective and eye-lens of a microscope are 1 cm and 5 cm respectively. If the magnifying power for the relaxed eye is 45, then the length of the tube is
[CPMT 1979]
Options:
A) 30 cm
B) 25 cm
C) 15 cm
D) 12 cm
Show Answer
Answer:
Correct Answer: C
Solution:
By using $ {m _{\infty }}=\frac{({L _{\infty }}-f _{o}-f _{e}).D}{f _{o}f _{e}} $
$ \Rightarrow 45=\frac{({L _{\infty }}-1-5)\times 25}{1\times 5}\Rightarrow {L _{\infty }}=15cm $ .
