Question

Carbon-14 has a half-life of 5715 years. It is used to determine the age of

Answer 1

The sample of Carbon-14 after 28,575 years=0.001875 mg

Further explanation

General formulas used in decay:  

$\large{\boxed{\bold{N_t=N_0(\dfrac{1}{2})^{T/t\frac{1}{2} }}}$

T = duration of decay  

t 1/2 = half-life  

N₀ = the number of initial radioactive atoms  

Nt = the number of radioactive atoms left after decaying during T time  

Carbon-14 has a half-life of 5715 years, so t1/2=5715 years

A sample today contains 0.060 mg of carbon-14, so No=0.06 mg, then :

$\tt Nt=0.06(\dfrac{1}{2})^{28575/5715}\\\\Nt=0.06(\dfrac{1}{2})^5\\\\Nt=0.001875~mg$