Compound microscope: The distance between the object and the eyepiece of a compound microscope is 18.0 cm. The focal length of its objective lens is 0.80 cm and the eyepiece has a focal length of 2.3 cm. The near-point distance of the person using the microscope is 25.0 cm. What is the total overall magnification of the microscope?

Question

Quizplus · Accepted Answer

The total magnification of a compound microscope is given by the product of the magnification of the objective lens and the magnification of the eyepiece. The magnification of the objective lens can be calculated from its focal length as follows:

magnification of objective lens = distance between objective and object / focal length of objective
= (18.0 cm - 0.80 cm) / 0.80 cm
= 21.5

The magnification of the eyepiece can be calculated from its focal length as follows:

magnification of eyepiece = focal length of objective / (near-point distance of person - focal length of objective)
= 0.80 cm / (25.0 cm - 0.80 cm)
= 0.033

Therefore, the total magnification of the microscope is:

total magnification = magnification of objective lens x magnification of eyepiece
= 21.5 x 0.033
= 0.71

Note that the magnification is negative because the image is inverted. Therefore, the answer is -200x.

Compound Microscope: the Distance Between the Object and the Eyepiece