A collector holds a convex lens of focal length 8.0 cm at a distance of 5.0 cm above a stamp…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A collector holds a convex lens of focal length at a distance of above a stamp. The stamp is wide. Treat the lens as thin. Find the distance of the image from the lens (with its sign), the magnification, and the width of the image.
Need a reminder? The key ideaShow
For a thin lens, and , with distances from the optical centre and positive in the direction of the light. A real object has . The lens maker's formula is .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. , and the width of the stamp .
Plan. The thin lens formula gives . Then gives the size.
Step 1. The image distance. We want , so .
Step 2. The magnification. .
Step 3. The width. .
Answer: , and .
Check. The image is virtual, on the same side as the stamp, upright and larger. This is how a magnifying glass works.
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