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 magnification of the microscope?
A) -120
B) -184
C) -200
D) -360
E) -480

Question

Quizplus · Accepted Answer

Total magnification of a compound microscope is given by the product of the magnifying power of the eyepiece and objective lens. Magnifying power is the ratio of the angle subtended by the image and the angle subtended by the object at the eye.

Magnifying power of objective lens = (25 cm/0.80 cm) = 31.25
Magnifying power of eyepiece = (18.0 cm/2.3 cm) = 7.83

Total magnification = Magnifying power of objective lens × Magnifying power of eyepiece = (31.25) × (7.83) = 245.125 ≈ -200

Note that the answer is negative because the image formed by the microscope is inverted.

The Distance Between the Object and the Eyepiece of a Compound