Question

The rate of disintegration of a radioactive substance is ______ the number of atoms present at that time.

• A. directly proportional to
• B. inversely proportional to
  
• C. equal to
• D. independent of

Answer 1

Answer: (A)

directly proportional to

For a given element, the decay or disintegration rate is proportional to the number of atoms and the activity measured in terms of atoms per unit time. If "A" represents the disintegration rate and "N" is number of radioactive atoms, then the direct relationship between them can be shown as below:

$A\propto N$