Answer: Slow (thermal) neutrons captured by the nucleus.
- A Slow (thermal) neutrons captured by the nucleus
- B High-energy fast neutrons exclusively, since slow neutrons cannot be captured
- C High-energy gamma ray photons absorbed by the nucleus
- D Alpha particles fired directly at the uranium nucleus
Correct answer: A. Slow (thermal) neutrons captured by the nucleus
Explanation: 235U is fissile and undergoes fission when it absorbs a thermal (slow, ~0.025 eV) neutron, splitting into fission fragments + 2-3 fast neutrons + energy.
Aqueous solutions of transition metal ions show characteristic colours caused by electrons absorbing visible light to jump between split d-orbitals; the exact colour depends on the metal, its oxidation state, and surrounding ligands.
Concept context
Transition metals (d-block) and lanthanides/actinides (f-block). Known for coloured compounds, variable oxidation states, complex formation, and catalytic properties. Frequently tested in JEE and NEET.