GCSE Physics Revision: Atomic Physics Alternative to Practical

At IGCSE Level, no experiments required from this Unit. 

Some pond water becomes contaminated by the release of radioactive waste. The radioactivity of a sample of the contaminated water is tested every week for 5 weeks.
The results are shown in the table below.

time/weeks      0      1     2           3    4         5       
activity/count   800      440       240       130        70   40

(a) Plot these values on the graph below.

Alternative to Practicle 13

(b) Draw the best curve through your points. 

(c) Define half-life of a radioactive material.
(d) Use your graph to find the half-life of the radioactive material in the sample. Show clearly on the graph how you obtained your answer.

(e) If the sample of contaminated water used in the test had been smaller, state how this would have affected, if at all,
            (i) the activity readings, …………….
            (ii) the value of the half-life. ………………….

(f) What do you understand about background radiation ?

(g) Why the count rate decreasing ?