# Compound Microscope Example

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20.309: Biological Instrumentation and Measurement

## Example 2: Compound microscope

There is a cool bacterium you want to study in closer detail so you want to build a microscope to see it. You are told that you can build a microscope by placing two positive lenses (having focal lengths $f_1$ and $f_2$) at a separation distance equal to the sum of their focal lengths as shown below.

A) Trace the rays to show how your microscope works and where the image is formed. Is the image real or virtual? upright or inverted? Note that this time the object is on the right and the image will form at the left.

B) Calculate how much magnification you get from this optical system.

C) Will your microscope still work if we change the distance between the lenses?

D) Does changing the distance between the lenses affect the amount of magnification you achieve?

Make sure you try to answer each question on your own before looking at the solutions below.

A) Trace the rays to show how your microscope works and where the image is formed. We will see that the image is real and inverted.

B) Calculate how much magnification you get from this optical system.

C) Will your microscope still work if we change the distance between the lenses?

D) Does changing the distance between the lenses affect the amount of magnification you achieve?