An object is placed to the left of a convex lens and on the optical axis. The ob

Question

An object is placed to the left of a convex lens and on the optical axis. The object is 34 cm from the lens and the focal length of the lens is 68 cm. What is the magnification of the image formed by the lens? You do not have to enter units for this problem.

I came up with 2...

First I used the lens formula

object distance s
image distance p
object distance 34

34x68/34-68
=2312/-34

=-68

Then
magnification = -p/s, since p is already negative (-68) it becomes positive
68/34
=2
Did I over complicate this? Any feedback would be great.

Explanation / Answer

i/v = 1/f + 1/u,

Here u = -34 cm, f = 68cm,

v = (68)*(-34)/34 = -68 cm.

M = (v/u) = -68/34 = -2, '-' indicates real.

So your answer is true.

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