(1) An experiment on the gamma rays from ¹³¹Ba, the gamma rays are allowed to fall on a lead radiator and on the photo electrons ejected are analysed in a magnetic spectrograph. The electrons fall into four groups with maximum at 1250, 1450, 2050 and 2500 gauss centimetre respectively. The binding energy of the K shall electrons in lead is 0.089 MeV what are the energies of the gamma rays?

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