Where on the electromagnetic spectrum is visible light found? a. between x-rays and uv rays b. between x-rays and gamma rays c. between infrared rays and uv rays d. between radio waves and microwaves

the decay of half of the nuclei only a half-life has passed ,  b) in rock time it is 1 108 years

Explanation:

The radioactive decay is given by

         N = N₀

If half of the atoms have decayed

       ½ N₀ = N₀

       ½ = ₀

       Ln 0.5 = - λ t

       t = - ln 0.5 /λ

The definition of average life time is

      = ln 2 / λ

       λ = ln 2 /  

       λ = 0.693 / 100 10⁶

       λ = 0.693 10⁻⁸ years

We replace

       t = -ln 0.5 / 0.693 10⁻⁸

       t = 10⁸ years

We see that for the decay of half of the nuclei only a half-life has passed

b) in rock time it is 1 108 years