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Medical X-ray sources often use radiation emitted when a tungsten atom is electrically excited such that a vacancy occurs in the 1s orbital. When a 2p electron subsequently drops to the 1s orbital, an X-ray is emitted with a wavelength of 2.09 x 102 nm. The energy difference between the 2p --> 1s in a tungsten atom is__ 10-19 J. Just give the absolute value of the difference