Iodine-131 has a half-life of 8.02 days. What is its decay constant, lambda, in units of per day?

1. The decay constant is lambda equals about 0.693 divided by the half-life. 2. Substitute the half-life of 8.02 days: lambda = 0.693 divided by 8.02. 3. Dividing gives lambda of about 0.0864 per day. 4. 0.0432 per day is half this value, and 0.173 per day is double it. 5. 8.02 per day simply repeats the half-life value rather than dividing it into 0.693. 6. So 0.0864 per day is correct. _Source: OpenStax Physics (CC BY 4.0), Ch 22 "The Atom", section 22.3 Half Life and Radiometric Dating_