**Solutions: Radioactivity Questions**

**Q11. **

(a) Suggest two reasons why an particle causes more ionization than a particle of the same initial kinetic energy.

An alpha particle has much more mass/momentum than beta particle

An alpha particle has twice as much charge as a beta particle

An alpha particle travels much slower than a beta particle

**(2 marks MAX) **

(b) A radioactive source has an activity of 3.2 × 10^{9} Bq and emits particles, each with kinetic energy of 5.2 MeV. The source is enclosed in a small aluminium container of mass 2.0 × 10^{–4} kg which absorbs the radiation completely.

(i) Calculate the energy, in J, absorbed from the source each second by the aluminium container.

**In one second** 3.2 × 10^{9} alpha particles are emitted.

Total energy emitted = 3.2 × 10^{9} x 5.2 x 10^{6} x 1.6 x 10^{-19} J

= 2.66 x 10^{-3}

= 2.7 x 10^{-3} J = 2.7 mJ

This energy is absorbed by the container so

energy absorbed = 2.7 mJ

(ii) Estimate the temperature rise of the aluminium container in 1 minute, assuming no energy is lost from the aluminium.

*specific heat capacity of aluminium = 900 J kg*^{–1} K^{–1}^{}

Heat gained by container = mc

**In one minute** - heat gained = 60 x 2.7 x 10^{-3} J = 0.162 J

= 0.162/(2.0 × 10^{–4} x 900)

Temperature rise = 0.90 K

**(5 marks)**

**(Total 7 marks)**