Question

When the quantity of a radioactive substance is increased two times, the number of atoms disintegrating per unit time is :

• A. doubled
• B. increased by square of two
• C. increased but not to a great extent
• D. not affected

Answer 1

The correct option is A doubled

Radioactive disintegration obeys first order reaction kinetic, i.e. rate of reaction is directly propotional to the initial amount.

$-\frac{dN}{dt}=kN$
Therefore, increasing the amount of radioactive substance two fold rate of disintegration is doubled.