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$x-$ray spectrometers often measure the energy of X $-$ray photons in units of kiloelectron volts $($keV$).$ This is the amount of energy gained by an electron after being accelerated by $1,000V$ of electricity. One keV is equivalent to $1\mathrm{.}60{10}^{-16}J.$ What is the wavelength of an X ay from a phosphorous atom with an energy of $3\mathrm{.}6$ keV $?$ Report your answer to $2$ significant figures.

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