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is magnification negative for a compound microscope at infinity

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- Thread starter RachaelD95
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- #1

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is magnification negative for a compound microscope at infinity

- #2

sophiecentaur

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Is this what you wanted? An inverted image implies a negative sign for the magnification.

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- The angular magnification of a microscope is 400X when the final image is at infinity. The optical tube length is 16cm and the focal length of the objective is 5mm. What is the focal length of the eyepiece?

They took the magnification to be -400x not sure why? The only thing I could take from it was that when its a compound microscope at infinity the magnification is negative.

- #4

sophiecentaur

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Wherever you choose to put the final (virtual) image, the magnification will still have the same sign. Using infinity just makes the calculation easier.

- The angular magnification of a microscope is 400X when the final image is at infinity. The optical tube length is 16cm and the focal length of the objective is 5mm. What is the focal length of the eyepiece?

They took the magnification to be -400x not sure why? The only thing I could take from it was that when its a compound microscope at infinity the magnification is negative.

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- #6

sophiecentaur

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I don't know where you got that from. Both the astronomical telescope (not the galilean telescope) and the microscope produce inverted real images - which is what the sign tells you. Also, I don't understand where you got the bit about 'focussed at infinity' as being special. You can easily focus a telescope at closer than infinity; for people with short sight and no glasses, for instance. The image is still the same way up! (i.e. inverted)

Are you using more than one source for you information? You may find that the sign has been omitted in one source.

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