An astronomical telescope has an angular magnification of magnitude ${\rm{5}}$ for distant objects. The separation between the objective and the eye-piece is ${\rm{36}}\,\,{\rm{cm}}$ and the final image is formed at infinity. The focal length ${f_0}$ of the objective and the focal length ${f_e}$ of the eye-piece are

${f_0} = 30\;\,{\rm{cm\;and\;}}\,{f_e} = 6\,\;{\rm{cm}}$

${f_0} = 45\;\,{\rm{cm\;and\;}}\,{f_e} = - \,9\,\;{\rm{cm}}$

${f_0} = - 7.2\;\,{\rm{cm\;and\;}}\,{f_e} = 5\;\,{\rm{cm}}$

${f_0} = 50\,\;{\rm{cm\;and\;}}\,{f_e} = 10\;\,{\rm{cm}}$

NEET UG PHYSICS MCQ: RAY OPTICS

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An astronomical telescope has an angular magnification of magnitude

\mathrm{5}

for distant objects. The separation between the objective and the eye-piece is

\mathrm{36}\,\,\mathrm{cm}

and the final image is formed at infinity. The focal length

{f_0}

of the objective and the focal length

{f_e}

of the eye-piece are

View answer and explanation

Correct option: D

{f_0} = 30\;\,\mathrm{cm\;and\;}\,{f_e} = 6\,\;\mathrm{cm}

Option D (

{f_0} = 30\;\,\mathrm{cm\;and\;}\,{f_e} = 6\;\,\mathrm{cm}

) is correct because it satisfies both the angular magnification and the separation conditions for an astronomical telescope.