Radioactivity is a phenomenon associated with MCQ with Answer and Explanation

Explanation:
Protium 0 neutrons, Deuterium 1, Tritium 2.

Explanation:
In uniform circular motion, speed remains constant but direction changes, so velocity (vector) changes. There is centripetal acceleration towards centre, so acceleration is not zero. Kinetic energy = ½mv², depends on speed, so remains constant. Thus, only speed is constant.

Explanation:
After n half-lives, activity reduces to (1/2)ⁿ of initial. Set (1/2)ⁿ = 1/16 ⇒ (1/2)ⁿ = (1/2)⁴ ⇒ n = 4 half-lives. Thus time = 4 × half-life. Memory aid: '1/2ⁿ remaining after n half-lives; 1/16 = 1/2⁴ ⇒ 4 half-lives'. This radioactivity calculation is frequently tested in competitive exams. Always express fraction as power of 1/2 to find half-life count. This problem assesses understanding of exponential decay without heavy computation.