K.C.S.E Physics Q & A - MODEL 2004PP2QN03

K.C.S.E Physics Q & A - MODEL 2004PP2QN03

​ Figure 4 shows the cross-section of a diffusion cloud chamber used to detect radiation from radioactive sources.

a) i) State one function of each of the following:
Alcohol
solid Co2
ii) When radiation from the source enters the chamber, some white traces are observed. Explain how these traces are formed and state how the radiation is identified.
iii) A leaf electroscope can also be used as a detector of radiation. State two advantages of the diffusion cloud chamber over the leaf electroscope as a detector.
b) i) Two samples of the same radioactive material have initial masses M and 2M respectively. On the axes provided, sketch the graph of activity versus time for each sample. Label the graph for each sample.

ii) A radioactive sample of half-life 130 days initially has 1.0 x 10²c radioactive atoms. Determine the number of radioactive atoms that have decayed after 390 days.

answers