Series limit is n=∞→1 so λ = 1/R ≈ 9.11×10⁻8 m ≈ 91.1 nm (≈91.2 nm).

X-ray imaging of the hand produces shadow-like images due to differential absorption, described here as shadow photography.

Potential energy is less negative (i.e. larger) at n = 2 than at n = 1, so the statement that it is 'less' (more negative) is false; option D is false.

A 1 TeV proton has γ ≈ 1000, giving β = sqrt(1 - 1/γ^2) ≈ 0.9999996, matching option B.

Mass defect = 2(1.0073)+2(1.0087)-4.0015 = 0.0305 u; energy = 0.0305 u × 931.5 MeV/u ≈ 28.4 MeV, matching option A.

George Gamow proposed an early form of the liquid-drop model for the nucleus; he is the Russian physicist referenced.

Surface radiotherapy for skin lesions commonly uses beta emitters like P-32 and Sr-90; the other pairs are not typical for skin cancer.

The photon is its own antiparticle, whereas the electron's antiparticle is the positron and the proton has a distinct antiparticle.

Higher energy particles travel further before losing energy, so track length increases with the incident particle's energy.

X-ray diffraction techniques are commonly used to study the arrangement of atoms in crystals.