what is a half life of a substance and how can you work it out.

A half life of a substance is the time it takes for the mass of a radioactive substance to decrease by half. Say you have 50g of carbon-14, you are looking for the amount of time it takes for the mass to reach 25g of this isotope.
Say we have 200g carbon-14, and it has a hypothetical half-life of 5 years. How much will be left after 20 years?So, we do 20/5=4, so we have 4 half lives undertaken. If a half life is dividing the mass by 2, each progressive half life also decreases the mass by dividing it by 2. So, we can think of dividing our original amount by 2^n, where n is the number of half lives passed. Therefore, we have 200/(2^4) or 200/16, which equals 12.5g remaining of carbon-14.

SW
Answered by Samuel W. Physics tutor

1529 Views

See similar Physics GCSE tutors

Related Physics GCSE answers

All answers ▸

Compare the wavelength, frequency and speed of an emitted and reflected microwave


Explain why a smoke alarm works by emitting and detecting alpha radiation instead of gamma or beta radiation.


(A-level but box won't let me change it from GCSE) A particle of charge q and initial speed v is stopped by a potential difference V in distance d and time t. What was its initial momentum?


A force is applied to a box of mass 2kg so that is accelerates at 2ms^-2. Find the force acting on the box and thus calculate the work done in moving the box 10m in the direction of the force.


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