A small finder telescope

PHYSICS · Subjective · Fermi University Physics · Optics & Photonics · Interference and diffraction · Interference and diffraction

Optics and Photonics, Ch Fraunhofer diffraction from apertures and gratings

Problem

A small

40\ \text{mm}

finder telescope, used in red light of

\lambda = 650\ \text{nm}

, clearly shows a double star of separation

4.5''

as two distinct points with an

8\ \text{mm}

eyepiece (

50\times

). The observer swaps to a

4\ \text{mm}

eyepiece (

100\times

), claiming the higher power will show the stars "even more clearly separated", implying the resolving power of the telescope has improved. Evaluate this using the Rayleigh criterion.

Related theory

Interference and diffraction

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