Please include all steps. A compound microscope has a distance of 14 cm between

Question

Please include all steps.
A compound microscope has a distance of 14 cm between lenses and anocular with a focal length of 7.9 mm. What power should theobjective have to give a total magnification of -370?
(must have correct significant figures) I have calculated fo to be 1.1974 (correct me if I am wrong).But the question want to know the power. How do I do this? isit1/fo? I submitted .835 and it is wrong. Is that because ofsignificant figures or something else. ? Please include all steps.
A compound microscope has a distance of 14 cm between lenses and anocular with a focal length of 7.9 mm. What power should theobjective have to give a total magnification of -370?
(must have correct significant figures) I have calculated fo to be 1.1974 (correct me if I am wrong).But the question want to know the power. How do I do this? isit1/fo? I submitted .835 and it is wrong. Is that because ofsignificant figures or something else. ?

Explanation / Answer

I saw your message only now. I think what you did are mostly correct except the lastpart. Since, M = m1.m2 = (-L/fo)x(25 cm/fe)          fo = -(14 cm/-370)x(25 cm/0.79 cm)                =+ 1.1974 cm (Do not leave out this unit) Power of a lens is P = 1/f To obtain powere in dioptres, the common SI unit, the valueof f must be in meters. So,   power, P = 1/(1.1974x10-2) =100/1.1974 = 83.5 dioptres. I think this is correct. However, to keep the the correct s.f., note that the givendata have only 2 s.f. Hence power, P = 84D This is positive(Converging lens.) I hope this is correct.

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