An object is placed 20.0 cm from a converging lens with focal length 15 cm.A concave mirror with focal length 10 cm is located 75 cm to the right of the lens as shown in the figure.Note: The figure is not drawn to scale.

-Determine the location of the final image.
A)48 cm to the right of the lens
B)96 cm to the right of the lens
C)30 cm to the left of the mirror
D)0.225 cm to the left of the mirror
E)0.225 cm to the right of the mirror

Question

An object is placed 20.0 cm from a converging lens with focal length 15 cm.A concave mirror with focal length 10 cm is located 75 cm to the right of the lens as shown in the figure.Note: The figure is not drawn to scale.
 
-Determine the location of the final image.
A)48 cm to the right of the lens 
B)96 cm to the right of the lens 
C)30 cm to the left of the mirror 
D)0.225 cm to the left of the mirror 
E)0.225 cm to the right of the mirror

Quizplus · Accepted Answer

Using the thin lens equation, we can find the location of the image formed by the converging lens:

1/f = 1/do + 1/di
1/15 = 1/20 + 1/di
di = 60 cm

This image becomes the object for the concave mirror. Using the mirror equation, we can find the location of the final image:

1/f = 1/do + 1/di'
1/-10 = 1/60 + 1/di'
di' = -30 cm

Note that the negative sign tells us that the final image is located to the left of the mirror. Therefore, the correct answer is C: 30 cm to the left of the mirror.

An Object Is Placed 20