Electromagnetic radiation can be classified into two major types depending on its ability to detach electrons from atoms: ionising and non-ionising. The aforementioned categorization is significant due to the effects of ionising radiation on human tissue (e.g. carcinogenesis). However, many students around the globe cannot distinguish these two types of electromagnetic radiation and as a result significant misconceptions arise regarding this topic (for example radiation emitted by mobile phones is considered by many students as ionising). Hence, in this paper a teaching approach specifically designed and implemented for the secondary education level is presented, based on the absorbed energy distribution by atoms/molecules in each radiation type. More specifically, the number of atoms/molecules that absorb equal doses of energy per unit mass can be used in order to explain the difference in the effects caused by the two abovementioned radiation types. Also, two analogies from classical mechanics are presented to provide a full insight into the energy distribution concept from a teaching perspective.