# JEE Main & Advanced Physics Ray Optics Reflecting Telescope

Reflecting Telescope

Category : JEE Main & Advanced

Reflecting telescopes are based upon the same principle except that the formation of images takes place by reflection instead of by refraction.

If ${{f}_{o}}$ is focal length of the concave spherical mirror used as objective and ${{f}_{e}},$ the focal length of the eye-piece, the magnifying power of the reflecting telescope is given by $m=\frac{{{f}_{o}}}{{{f}_{e}}}$

Further, if D is diameter of the objective and d, the diameter of the pupil of the eye, then brightness ratio $(\beta )$ is given by $\beta =\frac{{{D}^{2}}}{{{d}^{2}}}$

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