Physics - Nuclear Physics (9 of 22) Radioactive Activity (aka Decay Rate)

[@aaronreybonaobra9109]

I swear this guy knows everything

[@jdetres01]

your bow tie helped me listen better btw. i also love that you showed the few times you made a mistake and how you found out it was a mistake, and humbly corrected it. seeing someone do something completely perfect 100% of the time doesn't help people failing at the subject 90% of the time. so just seeing you forget the negative sign or even finishing the equation on the wrong line helped me see if i were to make a mistake, HOW to correct it! your teaching is more valuable than you may know and i wanted you to know that.

[@HaiderAli-nj7tv]

Sir at 1:17 why did you multiply negative lambda with the right side of your equation?How, is it some kind rule? I am from cie a levels they never taught us anything like ddt you did on both sides. I think i have asked a very dumb question.

[@MichelvanBiezen]

Not a dumb question at all. Sometimes we just don't see something. Happens all the time to me as well. When taking the derivative of an exponential function: d/dt (e^-at) = -a e^-at

[@DarknessIsThePath]

If I at the beginning get the decay rate of something, let's say 3070 decays/s in 500g of a sample, and carbon provides 225bq/kg, when you have to calculate the age of the sample, do you always have to take the ratio of the sample to the carbon one?

[@MichelvanBiezen]

Yes. You have to use the ratio of the mass of your sample to the mass of the object for which you know the reference decay rate.

[@DarknessIsThePath]

Nice, thanks for the answer.

[@aparna8577]

this was really insightful, thank you sir!

[@MichelvanBiezen]

Glad it was helpful!

[@sophielynn9198]

Sir, where does the minus sign go in the final answer?

[@MichelvanBiezen]

The minus simply indicates that the number of radioactive atoms is decreasing. But when we want to express the number of decays per second, it doesn't make any sense to keep the negative sign. (you can't have negative decays per second)

[@ahmadtheaviationlover1937]

@@MichelvanBiezen another way that the minus sign is used for is on logarithms and finding the reciprocal of a value

[@khushijain4969]

Why did you not mutiply e^-lambda/t to the last equation . That also consists of the rate of decays ?!

[@MichelvanBiezen]

We did. N(t) is the function with the exponent.

[@khushijain4969]

@@MichelvanBiezen but you just multiplied the no. Of nucleons and not the exponent in your calculations

[@MichelvanBiezen]

@@khushijain4969 Yes, when t = 0, the exponential part equals 1.

[@philipli1206]

You are my Savior ! Thank you very much ! Very clear !

[@rosakuppelapolye7823]

Where did you get the 0.693?

[@thomaswilson1107]

The time required for half of the original population of radioactive atoms to decay is called the half-life. The relationship between the half-life, T1/2, and the decay constant is given by T1/2 = 0.693/λ. (Copied off of Britannica)

[@curiash]

@@thomaswilson1107 correct

[@yassinedownpourz]

ln(2)

[@Svajok]

Hey! i thought all your videos on this topic are very clear and straightforward! Also arranged well, and i revised pretty well from them, thanks a lot

[@MichelvanBiezen]

You are welcome. Thanks for the comment.

[@curtpiazza1688]

Excellent!

[@MichelvanBiezen]

Glad you liked it!

[@hallahkhalil3027]

is this GCSE or A level

[@MichelvanBiezen]

It is not specifically geared towards any specific test, but the videos cover the key concepts of all physics.

[@danielvanderstruis1516]

legend

[@MichelvanBiezen]

Glad you like our videos. 🙂

[@judeohaji638]

How is carbon 14 one trillion of carbon 12 Why is trillion?

[@MichelvanBiezen]

it is the relative abundance