- #1
angelelizabeth
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Homework Statement
A lens of focal length 0.8m is 1.0 m to the left of a mirror of focal length -0.500m. An object is placed 1.00 m to the left of the lens. Light goes through the lens, bounces from the mirror, and goes through the lens again, this time from the right.
Homework Equations
1/f=1/di+1/do
The Attempt at a Solution
(THIS IS FROM THE OFFICIAL SOLUTION MANUAL, I AM CONFUSED ON PART OF THE ANSWER TOWARDS THE END)
1/di1=1/f1-1/do1
1/di1=1/0.8-1/1
di1=4.0 m
This image is 3 meters behind the mirror, so do2 for the mirror is -3.0 m.
1/di2=1/f2-1/do2
1/-0.5-1/-3=1/di2
di2= -0.6 m
This image is behind the mirror.
THIS IS WHERE I GET CONFUSED:
di3 (for the lens)=1+0.6m=1.6m
1/di2=1/f1-1/do3=1/0.8-1/1.6
di3=1.6m
In this instance, why is di3 postive 1.6 m instead of negative 1.6 meters? The "object" is to the right of the lens, so shouldn't di3 be negative?