The second stage is to combine all electromagnetic waves in one spectrum. In addition, the teacher can give students assignments to develop their own spectrum structures based on other principles. This method was used by the ancient Incas. After quipus are constructed, groups can exchange them and try to decipher the coded information by analyzing how the strings are grouped together, how many strings there are in each group, and according to what pattern the knots are arranged. Here is an example of an electromagnetic spectrum quipu based on frequency.
First string represents the speed of light.
It is considered to be a key string that gives the idea of how to insert numbers with scientific notations using different types of knots. The next, and perhaps, central part of this unit is a detailed description of each type of radiation. To increase the efficiency and to avoid repetition, it is logical to organize the whole process in the form of independent work in small groups. The whole class is divided into six groups, which are assigned to investigate a type of radiation in accordance with a certain format. In order to emphasize astronomical issues related to electromagnetic radiation, it would be helpful, for example, to have a poster contest.