With reference to the radioactivity, which of the following statements is/are correct ? 1). Radioactivity is a nuclear property. 2). Hydrogen bomb is prepared on the principle of nuclear fission. Select the correct answer using the codes given below. Codes :

Statement 1 is correct. Radioactivity is the spontaneous emission of alpha, beta or gamma radiation from an unstable nucleus. It depends only on the nucleus's internal configuration, not on chemical bonding, temperature, pressure or physical state. That is why it is classed as a nuclear property, and why Becquerel's and the Curies' work marked a turning point in atomic physics.

Statement 2 is wrong. A hydrogen bomb works on nuclear fusion, the joining of light nuclei such as deuterium and tritium to form helium and release energy. The fission principle belongs to the atom bomb, which uses uranium-235 or plutonium-239. In a thermonuclear weapon, a fission explosion serves as the trigger that creates the temperature and pressure needed to start fusion in the secondary stage.

• Statement 1: correct, since radioactivity originates in the nucleus.
• Statement 2: incorrect, since the hydrogen bomb is based on fusion, not fission.

Only statement 1 is correct, so the answer is A. The core concept is the difference between fission and fusion and the physics behind nuclear weapons. For Mains, this connects to India's nuclear doctrine, the NPT and CTBT debates, and the energy question of fission reactors versus fusion research.

Trap: candidates see "hydrogen" and "nuclear" together and assume fission, or they mix up the atom bomb and the hydrogen bomb. Remember that the hydrogen bomb is a fusion device, with fission used only as its trigger.