Photographic ate Magnetic Field T P XXXX XXXX Collimator Radioactive Element Apparatus similar to that used by henri becquerel to determine the magnetic deflection of radioactive decay products. The magnetic field is perpendicular to the direction of motion of the decay productsApparatus similar to that used by Henri Becquerel to determine the magnetic deflection of radioactive decay products. The magnetic field is perpendicular to the direction of motion of the decay products