Question

1/32nd of a radioactive element's atoms remain in a lunar rock sample. How many half lives old is the rock?

A. 1

B. 2

C. 3

D. 4

E. 5

Answer 1

E. 5

Step-by-step explanation:

N₀ = initial total number of radioactive elements number

N = Number of atoms of radioactive element after "n" half lives = N₀ /32

n = number of half lives

Number of atoms of radioactive element after "n" half lives is given as

`N = N_(o)\left ( (1)/(2) \right )^(n)`

inserting the values

`(N_(0))/(32) = N_(o)\left ( (1)/(2) \right )^(n)`

`(1)/(32) = \left ( (1)/(2) \right )^(n)`

n = 5