55 MeV a-particles are incident nomally upon a target of gold foil 1.0 µm thick. A fraction 1 in 108 per second was scattered through an angle of 60° and detected by a scintillation detector of area 25 mm? at a distance of 50 mm. Calculate: i) The number of the nuclei per unit volume in the target ii) The size of the solid angle dN (with its proper unit) subtended by the detector. iii) The atomic number of the gold (gold has atomic mass 197 u and density 1.93x10ʻkg/m³)

55 MeV a-particles are incident nomally upon a target of gold foil 1.0 µm thick. A fraction 1 in 108 per second was scattered through an angle of 60° and detected by a scintillation detector of area 25 mm? at a distance of 50 mm. Calculate: i) The number of the nuclei per unit volume in the target ii) The size of the solid angle dN (with its proper unit) subtended by the detector. iii) The atomic number of the gold (gold has atomic mass 197 u and density 1.93x10ʻkg/m³)