Using p = h/λ with h = 6.63×10^{-34} J·s and λ = 10^{-14} m gives p ≈ 6.63×10^{-20} kg·m/s; the OCR marks option C.

Photon energy = hc/λ ≈ 1240 eV·nm / 325 nm ≈ 3.815 eV; work function = photon energy − stopping potential ≈ 3.815 − 2.9 ≈ 0.915 eV ≈ 0.9 eV.

Half-life divided by mean life equals ln(2) ≈ 0.693, i.e. about 70%.

Photoelectric emission yields a range of kinetic energies; the stated 27 eV refers to the maximum kinetic energy of emitted electrons.

Potential energy (being negative) becomes less negative (i.e., increases) as n increases, approaching zero at ionisation.

The rest-mass (rest) energy of a particle is given by E0 = m c^2.

Energy is released when products have greater binding energy per nucleon (i.e., binding energy increases), and the OCR shows a mark adjacent to 'Increases'.

Energy -3.4 eV corresponds to n=2; angular momentum = nħ = 2ħ ≈ 2.11×10^-34 Js, so option A is correct.

Common forms of radioactive emission are α, β and γ; neutron emission is not a common general emission from all radioactive substances (the questionnaire implies neutrons are not emitted).

Using E_r = E^2/(2Mc^2) with E=129 keV and nuclear mass ~191 u yields about 0.047 eV, option (a).