An unknown radioactive source decays by emitting two different types of radiation. A simple experiment is performed to identify if they are alpha, beta, gamma or neutrons. Firstly, a radiation detector is placed 2 cm from the radioactive source and left to measure for 1 minute. Approximately 1000 counts are recorded. A piece of paper is then placed between the detector and source and another 1 minute measurement takes place. Approximately 400 counts are recorded. The piece of paper is replaced by 5 mm thick Aluminium and another 1 minute measurement takes place. Approximately 380 counts are recorded. The Aluminium is replaced by 1.5 cm of lead, and then only 10 counts are recorded in the following 1 minute measurement. Which can you deduce are the two most likely decay types for the source? *