To reduce uncertainty in momentum Δp, one increases position uncertainty Δx; using longer-wavelength light localizes less precisely and thus reduces momentum disturbance.

When U-238 absorbs a neutron it becomes U-239 (mass number increases by one), corresponding to option C.

In many nuclear reactions the initial step is formation of a compound nucleus before it decays or emits particles.

The OCR answer key marks option A; the text gives the deuteron binding energy as 2.8 MeV.

A practical blackbody is often a hollow cavity with its interior coated black and a small aperture, approximating ideal absorption/emission.

Wavelength scales as 1/Z^2; 1/4 = 1/Z^2 implies Z=2, which corresponds to He+.

Iron-56 (Fe56) is among the most tightly bound and thus most stable nuclei, so option D is correct.

The problem statement and provided answer hint indicate use of the Rutherford scattering formula and the block's answer key gives option D as the computed differential cross-section.

In Bohr model the fundamental quantum of angular momentum is h/2π, so h/2π corresponds to angular momentum.

Decay from actinium to thorium typically involves emission of an alpha particle (helium nucleus), so option C is correct.