Compound Microscope - Practice Questions & MCQ

Compound Microscope: 

A compound microscope is of two converging lenses called objective and eye lens. It is used to view magnified images of small objects on a glass slide. It can achieve higher levels of magnification than stereo or other low power microscopes and reduce chromatic aberration.

 Intermediate image is real and enlarged. The final image is magnified, virtual and inverted.

Here in the diagram 

  = Distance of object from objective (o), 

= Distance of image (A′B′) formed by objective from objective, 

= Distance of  A′B′ from eye lens, 

= Distance of final image from eye lens, 

=  Focal length of objective, 

= Focal length of eye lens.

Case 1: Final image is formed at D :  Magnification  and length of the microscope tube (distance between two lenses) is
Generally, object is placed very near to the principal focus of the objective hence The eye piece is also of small focal length and the image formed by the objective is also very near the eyepiece.

So   the length of the tube.
Hence, we can write

.
Case 2:  Final image is formed at Magnification

In terms of length    .

•  For large magnification of the compound microscope, both  should be small.
•  If the length of the tube of microscope increases, then its magnifying power increases.
• The magnifying power of the compound microscope may be expressed as  is  the magnification of  the  objective and   is magnifying the  of eyepiece.