Solution to 2001 Problem 13

We use the Rayleigh criterion, which states that the minimum angular separation \alpha_0 of two points sources such that an observer can tell them apart
is for a circular aperature with diameter D
\begin{align*}\alpha_0 = \frac{1.22 \lambda}{D}\end{align*}
where \lambda is the wavelength of the light.
Plugging in the given value for \lambda and \alpha_0, we can find that
\begin{align*}D = \frac{1.22 \lambda}{\alpha_0} = \frac{1.22 \cdot 600 \cdot 10^{-9} \mbox{ m}}{3 \cdot 10^{-5}} = 0.0839 \mb...
Therefore, answer (B) is correct.

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