Nuclear & Radioactivity — Set 4

Correct Answer: B. A sheet of paper

Option B is correct because alpha particles have low penetration and are stopped by paper. They lose energy quickly due to strong ionization in air. External alpha radiation is less penetrating, but internal exposure can be harmful.

Correct Answer: C. A thin sheet of aluminum

Option C is correct because beta particles are stopped by a thin metal like aluminum. They penetrate more than alpha particles but less than gamma rays. Using shielding reduces exposure to beta radiation.

Correct Answer: B. Thick lead or thick concrete

Option B is correct because dense and thick materials reduce gamma intensity effectively. Gamma rays are highly penetrating electromagnetic radiation. Shield thickness depends on energy and required safety level.

Correct Answer: D. +2e

Option D is correct because an alpha particle has two protons, giving it a +2e charge. This charge causes strong ionization and deflection in fields. Its mass is much larger than a beta particle.

Correct Answer: C. −1e

Option C is correct because beta minus radiation is an electron with charge −1e. It is deflected strongly due to its small mass. Beta emission increases the atomic number of the nucleus by 1.

Correct Answer: D. Photons with no mass and no charge

Option D is correct because gamma rays are photons and carry no charge. Their high energy allows deep penetration into materials. Gamma emission does not change atomic number or mass number.

Correct Answer: C. Ionization of gas leading to an electric pulse

Option C is correct because radiation ionizes the gas and triggers an electrical pulse. The counter counts pulses to indicate intensity. GM counters are widely used for detecting beta and gamma radiation.

Correct Answer: B. Condensation of vapor on ions

Option B is correct because ions created by radiation act as centers for vapor condensation. This forms tiny droplets along the particle path. Different radiations produce different track appearances.

Correct Answer: D. Cobalt-60

Option D is correct because cobalt-60 emits strong gamma rays used for therapy. Gamma rays can target deep tissues when properly focused. Medical use requires careful shielding and dose control.

Correct Answer: A. Technetium-99m

Option A is correct because technetium-99m is commonly used as a medical tracer. It emits gamma rays suitable for imaging with low patient dose. Tracers help study organ function without major surgery.