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    HELP!!!! I need urgent help.
    Two issues:
    One, when they ask for the initial number of nuclei, and you have worked out the decay constant, λ, already, you use the formula:

    delta N/delta t = -λN

    but in all the exam questions, when that comes up, they just use the initial activity for (delta N/delta t). Isn't that wrong? Cuz i usually use N at a single half life, so N is half of the original activity, and t is a half life. But thats wrong. WHHY?????????????????????

    Two, does anyone know what questions came up on Paper A of Jan 05, cuz I was not in school for the mocks, and my class mates are all stupid, lol.

    Please help me out, exam is in like 36hours and im stuck
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    The intial activity is the rate of change of N with respect to t. (dN/dt). by putting it equal to -λN, where λ is known to calculate N

    As the activity is constantly changing and obeys the laws of exponential decay you cannot simply calculate it as you suggest.

    That is if i understand what you are saying...
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    activity = decay constant * number of nuclei

    the decay constant is the chance that a nuclei will decay on one second, so this times the total number is, on average, the number of decays per second or the activity. A = λN
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    (Original post by mik1w)
    activity = decay constant * number of nuclei

    the decay constant is the chance that a nuclei will decay on one second, so this times the total number is, on average, the number of decays per second or the activity. A = λN
    Ah ok, now i get it. So are you 110% sure about the "A = λN" formula, cuz i've never heard of it, but then again my teacher is as old as Newton himself, so probably forgot alot.
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    yeah 100%
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    ITs right A=lambda*N chilllll
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    Sometimes that formula isnt accurate enough unless delta is REALLY tiny, you have to use

    N=Noe^(-λt)

    where N is number No is initial number e is the mathematical e t is time and λis decay constant

    It is the same formula for A (activity) if you replace N with A and No with Ao
 
 
 
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