Equation 6 · Part 2 · How Scientific Instruments and Metrology Actually Work

Symbol λ

d \;\approx\; \frac{0.61\,\lambda}{n\sin\alpha}

\lambda

What this part means

the wavelength of the illuminating radiation, and n $\sin$ $\alpha$ is the numerical aperture of the imaging system.

Its job in the formula

λ occurs above the fraction bar. The numerator is divided by the entire denominator below it.

Full expressionSymbol λArticle meaning

Where the article explains it

where $\lambda$ is the wavelength of the illuminating radiation, and n $\sin$ $\alpha$ is the numerical aperture of the imaging system.

The passage around this formula

…into its own optics. The achievable resolution of any imaging system with a circular aperture is bounded, in the simplest diffraction-limited approximation, by a form of the Rayleigh criterion: $d \;\approx\; \frac{0.61\,\lambda}{n\sin\alpha}$ . where $\lambda$ is the wavelength of the illuminating radiation, and n $\sin$ $\alpha$ is the numerical aperture of the imaging system. For visible light this caps optical microscopy at roughly 200 nanometres — far too coarse to resolve individual atoms, whose spacing in a solid is typically a few tenths of a…

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Learn the underlying idea

A variable is a named place for a value. Its letter is a local label: x can mean position in one formula and a data point in another.

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Sources cited in the article section

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