Uranium -238 has a half life of 4.5 billion years. How long will it take a 2g sample of U-238 to contain just 0.4g of U-238?

 

Radioactive decay is a process where the nucleus of an unstable atom, such as Uranium-238 loses energy by emitting radiation.

The half life is the average time it take for half the nuclei in a sample to undergo radioactive decay.

Given an initial sample of x with mass N(0). After a time t the mass of x left in the sample N(t) is given by:

N(t) = N(0).2-t/t1/2                (1)

Where t1/2 is the halflife. 

To answer the question we need to find t. Rearranging equation (1) we have:

- t1/2  log2[N(t)/N(0)] = t          (2)

subbing the values from the question into (2)

-4.5x10 log2 [0.4/ 2] = 10.4 billion years

 

Answered by Robert E. Physics tutor

12678 Views

See similar Physics A Level tutors

Related Physics A Level answers

All answers ▸

Explain in terms of the motion of the molecules of the gas why the volume of gas must increase if the pressure is to remain constant as the gas is heated.


What is the most effective use of the equation sheet?


Is the excitation and de-excitation of an electron from the ground state (of an atom) due to the collision of another particle (e.g. electron) an elastic collision or an inelastic collision.


The roar of a tiger in a zoo can be heard by visitors at the entrance, even though the tiger can not be seen because there is a hill in the way. Name and explain this effect.


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences