# Question #72f8f

##### 1 Answer

Jun 21, 2016

#### Answer:

One sixteenth part.

#### Explanation:

Half life means that half of the number of atoms you start with has decayed (i.e. emitted radiation):

**Iodine 131** has a half life of

- 1 half life = 1/2 left
- 2 half lifes = 1/4 left
- 3 half lifes = 1/8 left
- 4 half lifes = 1/16 left

For more complex calculations you can use the equation:

In which