IB Physics: Half Lives

Defines half life, introduces the radioactive decay curve, and relevant formulas. Solves several examples.
IB Physics Topic 7.2
Click JOIN to become a member of C. Doner’s IB Physics RUclips Channel, or become a patron by visiting / cdoner .
Level/Tier 1: $1.99 per month gives you access to a google sheet with a full updated, well organized, linked listing of all the videos and other resources such as notes, worksheets and solution sets.
Level/Tier 2: $4.99 per month gives you access to new videos. The new videos include IB style multiple choice and problem solving questions with full explanations, previews/reviews of the course content, and updates to the video lessons.
After becoming a member, go to bit.ly/donervidlist and request access to the video listing.
Many students have written to thank me for the success they had with their IB Physics exams and their IA or Extended Essay. Though the style is that of Khan Academy, the videos are more specific to the IB content, contain more simulations and interactive examples, and are performed by someone who has 25 years of experience teaching IB Physics, an MSc in Physics from a top University, and who was an NSERC scholar.
"I would just like to say a massive thank you to you for uploading your videos. I started the IB [and]decided to try HL Physics as it seemed interesting. It turned out to be very far from my forté and I was consistently getting 3s and 4s in tests and mock exams. So a few months before the exam period of this year, I began to panic...Then I discovered your channel. For four weeks prior to paper one, I virtually worshipped your videos, and worked along to them in my 'Big Book of Revision.' Last week, I received my results. Incredibly and almost unbelievably, I obtained a 6 in HL Physics. Not only that, but I was 3 marks off a 7."

[@carameldogs09898]

at 5:30 everytime you said the unit of time it changed!! haha It went from 3 hours to 6 days to 9 years :')

[@donerphysics]

Yes, my brain clutch was slipping that day. I added an annotation.

[@tiramisumandeln]

you are a DEMIGOD

[@JaZoN_XD]

HL3 pls... everytime i hear the words half-life whether it's math or physics or chemistry seriously. They just need to release it hahaha

[@oshasrahimi551]

In an old IB exam question, it is asked to find the decay activity after a certain amount of hours however, they also stated that there was average background activity present. In such case, how would you incorporate it into the equation of activity.
Thank you for these great videos.

[@donerphysics]

Subtract the background from any activities that you are given, and then determine from these values how long it took for the activity to half.

[@oshasrahimi551]

@@donerphysics Thank you for the reply! That is what I did and the answer was not correct apparently, the markscheme showed that they had included the b.a in the total initial activity and then multiplied the final answer by two. On the other hand in some other similar questions the answer was found by calculating it as normal which was what you are also showing in the video.

[@pyrodracoaureus8469]

I'm confused about probability and half-lives. I don't quite understand the connection between the two. I thought half-life is just defined as a set amount of time it takes for a particular substance to halve its original amount. I don't understand how probability is involved. Can you explain? Thanks and great video btw!

[@donerphysics]

If the probability of a single nucleus decaying were higher, the half life would be shorter. Just be aware that we don't know when an individual nucleus will decay, we can only talk about the probability of it decaying.

[@coolkid9206]

In my class, the teacher gave us another formula, N x e^(kt) where k = e^(1/halflife). Whats this formula about?

[@donerphysics]

This video is on integer half lives. There is another one with the other formula. N=No e ^ (llambda t) where llambda is called the decay constant. ruclips.net/video/hkZYGGCA6kQ/видео.html

[@canberkozsu4013]

What does it mean for a particle to decay ?

[@donerphysics]

It simply means that the nucleus is unstable and it emits a particle and becomes more stable.

[@Laithalnasser]

This video is missing a lot of information about Half-lives, such as the decay constant, Equations for Activity and Number of radioactive nuclei, background radiation, etc...

[@donerphysics]

That is HL material. Watch the videos for topic 12.2 including "The Decay Constant"

[@Laithalnasser]

@@donerphysics Alright. Thank you!