PhysicsBowl 2019 Q29

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PhysicsBowl 2019

29) We are told that a convex lens has a focal length of 50 mm. Now we need to figure out where an object should be placed such that an image with a magnification of 3. Magnification is a relation between the image distance and the object distance, so this could help us.

Where M is magnification, d[i] is image distance, and d[o] is object distance

Now using this, in combination with the lens equation we can solve for the object distance. The general lens equation describes the relationship between focal length, object distance, and image distance.

Where f is focal length, d[o] is object distance, and d[i] is image distance

As a reminder, this is a convex lens which means it is a converging lens and has a positive focal length.