To understand the concept of radioactive decay and calculate the percentage of remaining undecayed material after a certain time, we need to consider the half-life of the radioactive substance.


The half-life of a radioactive substance is the time it takes for half of the material to decay. It is a characteristic property of each radioactive element.


To calculate the percentage of remaining undecayed material after a certain time, we need to know the number of half-lives that have passed.

Let's assume we start with 100% of the radioactive material.

After the first half-life, half of the material will decay, and we will be left with 50% undecayed material.
After the second half-life, another half of the remaining material will decay, leaving us with 25% undecayed material.
After the third half-life, half of the remaining material will decay, leaving us with 12.5% undecayed material.
After the fourth half-life, another half of the remaining material will decay, leaving us with 6.25% undecayed material.

Therefore, after a time equal to four half-lives, the percentage of radioactive material remaining undecayed is 6.25%.


- The half-life of a radioactive substance is the time it takes for half of the material to decay.
- After each half-life, the remaining undecayed material is halved.
- After four half-lives, the percentage of remaining undecayed material is 6.25%.