Question

1) Define what is meant by the half - radioactive material.

2) Radioactive decay is a random process. Explain what this means.
3) The activity of radioactive sample is measured. The activity corrected for background radiation is found to be 240 Bq. The activity is measured again after 1 hour 30 minutes and is now 30 Bq. What is the half life of the sample?

Answer 1

1) Solution Refer to the Attachment

2)

• Radioactive decay is the set of various processes by which unstable atomic nuclei (Nuclides) emit subatomic particles (Radiation). ... This is a random process . it is impossible to predict the decay of individual atoms.

• Radioactive decay is the random process in which a nucleus loses energy by emitting radiation. This is usually in the form of alpha particles (Helium nuclei), beta particles (electrons or positrons), or gamma rays (high energy photons). The nucleus' energy reduces, making it more stable. In all decay processes mass, charge and lepton number are conserved.

• The activity A,A (Or number of decays per second) is given by:-

• A=λN

• where lambda,λ is the decay constant and N,N is the number of undecayed nuclei of that type. The number of remaining nuclei is:-

• N =N 0 e −λt

• where N 0 is the number of these nuclei at t equals , t=0.

• The half-life T1/2 of a sample is the time taken for half of the radioactive nuclei to decay:-

• T1/2 = In2/ λ .

3)

• Half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other nuclear species by emitting particles and energy) or, equivalently, the time interval required for the number of disintegrations per second of a radioactive .

Graph refer to the attachment .

Hope this helps you !!