Question

A sample of a material has 2000 radioactive particles in it today. Your great-grandfather measured 4000 radioactive particles in it 90 years ago. 90 years from today, how many radioactive particles will the sample have?

90 years from today, how many radioactive particles will the sample have?

___ Radioactive Particles

180 years from today, how many radioactive particles with the sample have?

___Radioactive Particles

Answer 1

Current no. of radioactive particles = 2000

During the time of grandfather = 4000

Applying the equation,

A = A0 e^(-lamda*t)

= 2000 = 4000 exp(-lamda*90years)

= 0.5 = exp(-lamda*90years)

= ln 0.5 = -lamda * 90 years

= lamda = 0.0077 year ^-1

1)so now radioactive particles 90 years from today

= A = Ao exp(-Lamda*t)

= A = 4000exp (- 0.0077*180)

=A = 1000 particle

2)After 180 years from present

A = Ao exp(-Lamda*t)

A = 4000exp (- 0.0077*270)

=A = 500 particles