12 12 A thin target (foil) of 24 Mg metal, with a thickness of 1.0 mg cm², is bombarded by a beam of alpha particles with an intensity of 2.0 × 106 particles s-1. The nuclear reaction between a 22- Mg nucleus and an alpha particle results in the transmutation of the 24 Mg atom, with the emission of a proton. If the total number of protons emitted from the target is 18 s-1, calculate the total cross-section for the reaction. (Note: Assume that a 24 Mg atom has an atomic mass of 24.0 u). 12 Calculate the velocity of recoil electrons when electromagnetic radiation of wavelength 1.0 μm is Compton scattered through an angle of 90°. Assume that the electrons are not scattered at relativistic energies.

12 12 A thin target (foil) of 24 Mg metal, with a thickness of 1.0 mg cm², is bombarded by a beam of alpha particles with an intensity of 2.0 × 106 particles s-1. The nuclear reaction between a 22- Mg nucleus and an alpha particle results in the transmutation of the 24 Mg atom, with the emission of a proton. If the total number of protons emitted from the target is 18 s-1, calculate the total cross-section for the reaction. (Note: Assume that a 24 Mg atom has an atomic mass of 24.0 u). 12 Calculate the velocity of recoil electrons when electromagnetic radiation of wavelength 1.0 μm is Compton scattered through an angle of 90°. Assume that the electrons are not scattered at relativistic energies.