I have attached a picture of an extract I read on Wikipedia (also in the AQA A-Level Physics specification and textbook). It says that 1/10000 alpha particles deflected in the alpha particle scattering experiment and therefore, the probability is 1/10000 that it will deflect (more than 90 degrees). It then goes on to say that for n layers of atoms, the probability is 1/10000n. This doesn't make sense to me. If the number of layers increases, that means the probability of deflection is getting smaller.
Surely if there are more layers, deflection is more likely?