(a) Draw the ray diagram showing the formation of image by a compound microscope. (b) Show that in order to achieve large magnification in a compound microscope the magnitude of focal length of objective and eye piece should be small.
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(A) : Compound microscope is consist of two convex lenses, one object of very small focal length with short aperture and one eyepiece, E of moderate focal length and large aperture. The ray diagram showing the formation of image by a compound microscope is shown in the diagram.
(B) : The Magnifying power, M=me×mo where me and mo are the individual magnifying powers o objective and eye lens.
M=u0v0(1+feD)--------- (1) when the final image is at near point.
M=u0v0×feD-----------(2) when the final image is at the infinity.
From the equations (1) and (2) it is clear that for achieving a large magnification the focal length fe must be small. Hence the answer.
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