A compound microscope is made with an objective lens (
= 0)90 cm)and an eyepiece (
= 1)1 cm).The lenses are separated by a distance of 10 cm.If an object is 1.0 cm in front of the objective lens,where will the final image of the eyepiece be located?
A)−30
B)−15
C)−23
D)−11
E)−9

Question

A compound microscope is made with an objective lens ( 
= 0)90 cm)and an eyepiece ( 
= 1)1 cm).The lenses are separated by a distance of 10 cm.If an object is 1.0 cm in front of the objective lens,where will the final image of the eyepiece be located?
A)−30 
B)−15 
C)−23 
D)−11 
E)−9

Quizplus · Accepted Answer

Using the thin lens equation, 1/f = 1/di + 1/do, we can first find the location of the image created by the objective lens. 
(1/90) = (1/di) + (1/1) 
Solving for di, we get di = 0.98 cm. 
This image then becomes the object for the eyepiece: 
(1/1) = (1/di') + (1/10) 
where di' is the location of the final image. 
Solving for di', we get di' = -11 cm. Negative answer indicates that the image is virtual and upright. Thus, the final image of the eyepiece will be located 11 cm behind the eyepiece, in the same direction as the object. Therefore, the correct answer is D (-11).

A Compound Microscope Is Made with an Objective Lens