large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb_43
large/12904/worldswithinworlds_v1-3_1904_librivox_64kb_mp3/worldswithinworlds_01_asimov_64kb
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12904
He measured the exact wavelength of the characteristic X rays by reflecting them from certain crystals. In crystals, atoms are arranged in regular order and at known distances from each other. HE MEASURED THE EXACT WAVE LENGTH OF THE CHARACTERISTIC X RAYS BY REFLECTING THEM FROM CERTAIN CRYSTALS IN CRYSTALS ATOMS ARE ARRANGED IN REGULAR ORDER AND AT KNOWN DISTANCES FROM EACH OTHER
odel of the “nuclear atom” is still accepted today. Atomic Numbers Since the atom consisted of a positively charged nucleus at the center, and a number of negatively charged electrons outside, the next step was to find the exact size of the nuclear charge and the exact number of electrons for the different varieties of atoms. The answer came through a line of research that began with the English physicist Charles Glover Barkla (1877-1944). In 1911 he noted that when X rays passed through atoms, some were absorbed and some bounced back. Those that bounced back had a certain ability to penetrate other matter. When the X rays struck atoms of high atomic weight, the X rays that bounced back were particularly penetrating. In fact, each different type of atom seemed associated with reflected X rays of a particular penetrating power, so Barkla called these “characteristic X rays”. In 1913 another English physicist, Henry Gwyn-Jeffreys Moseley (1887-1915), went into the matter more thoroughly. INCE THE ATOM CONSISTED OF A POSITIVELY CHARGED NUCLEUS AT THE CENTRE AND A NUMBER OF NEGATIVELY CHARGED ELECTRONS OUTSIDE THE NEXT STEP WAS TO FIND THE EXACT SIZE OF THE NUCLEAR CHARGE AND THE EXACT NUMBER OF ELECTRONS FOR THE DIFFERENT VARIETIES OF ATOMS THE ANSWER CAME THROUGH A LINE OF RESEARCH THAT BEGAN WITH THE ENGLISH PHYSICIST CHARLES GLOVER BARCLAY EIGHTEEN SEVENTY SEVEN TO NINETEEN FORTY FOUR IN NINETEEN ELEVEN HE NOTED THAT WHEN X RAYS PASSED THROUGH ATOMS SOME WERE ABSORBED AND SOME BOUNCED BACK THOSE THAT BOUNCED BACK HAD A CERTAIN ABILITY TO PENETRATE OTHER MATTER WHEN THE X RAYS STRUCK ATOMS OF HIGH ATONIC WEIGHT THE X RAYS THAT BOUNCED BACK WERE PARTICULARLY PENETRATING IN FACT EACH DIFFERENT TYPE OF ATOM SEEMED ASSOCIATED WITH REFLECTED X RAYS OF A PARTICULAR PENETRATING POWER SO BARKLA CALLED THESE CHARACTERISTIC X RAYS IN NINETEEN THIRTEEN ANOTHER ENGLISH PHYSICIST HENRY GWEN JEFFREYS MOSELY EIGHTEEN EIGHTY SEVEN NINETEEN FIFTEEN WENT INTO THE MATTER MORE THOROUGHLY
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