A school observatory's Newtonian telescope has an objective mirror of diameter and is…

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Geometrical optics and imaging · Geometrical optics and imaging

Optics and Photonics, Ch Stops, pupils and optical instruments

Problem

A school observatory's Newtonian telescope has an objective mirror of diameter

200\ \text{mm}

and is set to a magnification of

80\times

. A starter refractor for a beginner has an objective of diameter

100\ \text{mm}

, also set to

80\times

by choosing a suitable eyepiece. A student claims that because both instruments magnify a faint star by exactly

80

times, they must reveal it equally well. ((a)) Explain what is wrong with the student's reasoning. ((b)) Find the factor by which one telescope out-performs the other in the light it collects from the star.

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