Isotope X is radioactive. It decays by alpha-particle emission to a stable isotope.

1. (a)State how a nucleus of X changes when it emits an alpha-particle.[2]
2. (b)(i)There is a radiation detector in a laboratory where there are no radioactive samples. The detector is switched on and shows an average count rate of 22 counts/minute. State why the radiation detector shows a count rate.[1]
3. (b)(ii)A sample of isotope X is placed 2cm from the detector and the reading displayed is 8000 counts/minute. The sample is moved a distance of 10cm from the detector. The reading returns to an average value of 22 counts/minute. Explain why the reading returns to the original value.[2]
4. (c)(i)An alpha-particle passes into a region where there is a magnetic field. In the magnetic field, a force acts on the alpha-particle so that it follows a circular path. Fig. 6.1 shows that the particle passes through point J. [Figure 6.1] On Fig. 6.1, draw an arrow through point J to show the direction of the force on the alpha-particle at J.[1]
5. (c)(ii)Determine the direction of the magnetic field and mark a tick in the box (✔) that indicates this direction. to the left to the right towards the top of the page towards the bottom of the page into the page out of the page[1]
6. (c)(iii)Explain whether this force does work on the alpha-particle as the particle moves along the circular path.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.