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?
A) -120 x
B) -184 x
C) -200 x
D) -360 x
E) -480 x

Question

Quizplus · Accepted Answer

The total overall magnification of a compound microscope is given by:
Magnification = (magnification of objective lens) x (magnification of eyepiece)
The magnification of the objective lens is given by:
magnification of objective lens = focal length of objective lens / (distance between object and objective lens)
magnification of objective lens = 0.80 cm / (18.0 cm - 0.80 cm)
magnification of objective lens = 0.0465x
The magnification of the eyepiece is given by:
magnification of eyepiece = 1 + (near-point distance / focal length of eyepiece)
magnification of eyepiece = 1 + (25.0 cm / 2.3 cm)
magnification of eyepiece = 11.87x
Therefore, the total overall magnification is:
Magnification = (magnification of objective lens) x (magnification of eyepiece)
Magnification = (0.0465x) x (11.87x)
Magnification = 0.553x
The negative sign indicates that the image is inverted. Therefore, the best choice is C, which gives a total overall magnification of -200x.

The Distance Between the Object and the Eyepiece of a Compound