Question 153: Ray Optics

Question

If we need a magnification of 375 from a compound microscope of tube length 150 mm and an objective of focal length 5 mm, the focal length of the eye-piece, should be close to :

Accepted Answer

Case 1 :
Near Ã¢ÂÂ point adjustment
M.P = $${L \over {{f_0}}}\left( {1 + {D \over {{f_e}}}} \right)$$
$$ \Rightarrow $$ 375 = $${{150} \over 5}\left( {1 + {{250} \over {{f_e}}}} \right)$$
$$ \Rightarrow $$ f
e
= 21.7 mm $$ \approx $$ 22 mm
Case-2 :
If final image is at inifinity
M.P = $${L \over {{f_0}}}\left( {{D \over {{f_e}}}} \right)$$
$$ \Rightarrow $$375 = $${{150} \over 5}\left( {{{250} \over {{f_e}}}} \right)$$
$$ \Rightarrow $$ f
e
= 20 mm

Answer

22 mm

Answer

12 mm

Answer

33 mm

Answer

2 mm

Ray Optics

If we need a magnification of 375 from a compound microscope of tube length 150 mm and an objective of focal length 5 mm, the focal length of the eye-piece, should be close to :

Choose the correct answer: