= George Biddell Airy
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<George Biddell Airy> calculated the <diffraction> pattern produced by a circular <aperture>. His treatment explains why an unresolved <star> appears as a central bright region surrounded by rings even in an otherwise ideal <optical telescope>.
In modern notation, the first dark ring occurs at an <angle> approximately $1.22\lambda/D$, where $\lambda$ is the <wavelength> and $D$ the <aperture> <diameter>. Doubling the <diameter> halves this angular scale at fixed <wavelength>. The <Airy disk> thus connects the wave nature of <light> to the resolving power of an instrument; simply increasing magnification cannot remove the underlying <diffraction> pattern.<On the Diffraction of an Object-glass with Circular Aperture by George Biddell Airy>[Original circular-aperture calculation and first dark-ring result; reproduced original in appendix, pp. 62–66 of annotated document]{ref}
His name also appears in the <Airy functions>, another recurring mathematical tool in wave and differential-equation problems.
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{title=Portrait of <George Biddell Airy>}
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