Question

In a compound microscope, the focal length of the objective and the eye lens are 2.5 cm and 5 cm respectively. An object is placed at 3.75 cm before the objective and image is formed at the least distance of distinct vision, then the distance between two lenses will be (i.e. length of the microscopic tube)
A) 11.67 cm B) 12.67 cm C) 13.00 cm D) 12.00 cm

Answer 1

given

fe=3cm

and  
           

fo=1.2cm


           

uo=1.25cm


           

ve=∞


From , 

1/uo+1/vo=1/fo

, 
we get

1/vo=1/1.2−1/1.25

vo=30cm  


Magnification of microscope

m=vo/uo(1+Dfe)


m=30/1.25(1+253)≃200

           .