Question 1

Paper 2Easy7 marks

A sealed radioactive sample contains NN undecayed nuclei at time tt Figure 1 shows how NN changes with time.

024681012024681012Time, t / hNumber of undecayed nuclei / 105
(a)

Use Figure 1 to state the number of undecayed nuclei at t=0t=0 and at t=4.0 ht=4.0\ \text{h}

[2]
(b)

Using your values from (a) and the radioactive decay law N=N0e−λtN=N_0e^{-\lambda t} determine the decay constant λ\lambda Give its unit.

[2]
(c)

Determine the number of undecayed nuclei in the sample at t=10.0 ht=10.0\ \text{h} Use the decay law and your value of λ\lambda from (b).

[3]

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