An astronomical refracting telescope will hav | vedclass

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(D) For an astronomical telescope,the angular magnification $M$ is given by $M = \frac{f_o}{f_e}$,where $f_o$ is the focal length of the objective len

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large focal length and large diameter

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(D) For an astronomical telescope,the angular magnification $M$ is given by $M = \frac{f_o}{f_e}$,where $f_o$ is the focal length of the objective lens and $f_e$ is the focal length of the eyepiece.To achieve a large angular magnification,the objective lens must have a large focal length $f_o$.The angular resolution of a telescope is given by $	heta = \frac{1.22 \lambda}{D}$,where $D$ is the diameter of the objective lens and $\lambda$ is the wavelength of light.To achieve high angular resolution,the value of $	heta$ must be small,which implies that the diameter $D$ of the objective lens must be large.Therefore,an astronomical refracting telescope requires an objective lens with a large focal length and a large diameter.

An astronomical refracting telescope will have large angular magnification and high angular resolution when it has an objective lens of

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