The Student Room Group

Radioactive decay question ( Nuclear physics )

I'm having trouble working out the answer to this question (in attachment below).
I worked out lambdalambda using this equation: lambda=ln/t−(1/2) lambda = ln/t^-(1/2)
Then substituted the value of lambda in N=N0e−λ(t) N = N0e^-\lambda (t)
(edited 5 years ago)
PH05_03.png16.3KB
λ=ln2t12 \lambda = \dfrac{ \text{ln} 2 }{t_{\frac{1}{2}}}

Decay constant is found

hence use N=N0e−λt N = N_0 e^{- \lambda t}
95% has decayed, so 5% is left. So
put N = 0.05N0
Reply 2
Avatar for Anon#9
Anon#9
OP
17
Original post by BobbJo
λ=ln2t12 \lambda = \dfrac{ \text{ln} 2 }{t_{\frac{1}{2}}}

Decay constant is found

hence use N=N0e−λt N = N_0 e^{- \lambda t}
95% has decayed, so 5% is left. So
put N = 0.05N0

I used N=0.95N0 N= 0.95N_0
But they've asked the time taken for 95% of the sample to decay, not 5%, how did you derive this?
Original post by Saman_B9
I used N=0.95N0 N= 0.95N_0
But they've asked the time taken for 95% of the sample to decay, not 5%, how did you derive this?

λ=ln2t12 \lambda = \dfrac{ \text{ln} 2 }{t_{\frac{1}{2}}}

Decay constant is found

hence use N=N0e−λt N = N_0 e^{- \lambda t}
95% has decayed, so 5% is left. So
put N = 0.05N0

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you