Question

When the length of a microscope tube increases, its magnifying power :

• A. decreases
• B. increases
• C. does not change
• D. can't say

Answer 1

Answer: (B)

increases

Magnification in microscpoe is $m=-\frac{l}{f_0}\frac{D}{f_e}$
where, $l$ is length of tube and $D$ is least distance for clear vision
$f_0$ is focal length of objective
$f_e$ is focal length of eyepiece.
So, as $l$ increases m increases.
Hence, magnifying power of microscope increases with increase in tube length.