Question

After 1 hour, `(1/8)^"th"` of the initial mass of a certain radioactive isotope remains undecayed. The half-life of the isotopes is ______.

Options

• 10 minutes

• 20 minutes

• 40 minutes

• 80 minutes

Answer 1

After 1 hour, `(1/8)^"th"` of the initial mass of a certain radioactive isotope remains undecayed. The half-life of the isotopes is 20 minutes.

Explanation:

`1/8 = 1/2^3`

` therefore` n = 3

t = 1 hour = 60 minutes

` therefore "T" = "t"/"n" = (60  "minutes")/3`

= 20 minutes