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$$ P=\frac{1}{f} $$

Telescope

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$$ M=\frac{F_1}{F_2}=\frac{\theta'}{\theta} $$

Parameters for a telescope

  1. Image scale $p=1/f$
  2. Collection area $A=\pi D^2/4$
  3. Focal ration $F=f/D$
  4. Diffraction limit $\theta=\lambda/D$ (single telescope) or $\theta=\lambda/D$ (interferometer)

Snell’s law

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Gratings interference

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