Experiences

Waves and coins can disappear. Science or magic?

M. Reyes LLácer Pérez

Spain

High Secondary School

Biology, Science

Teaching in class

Direct

When an earthquake occurs, and we study the seismic waves, we can see appear shadow areas on the planet where neither P nor S waves are received Although there are multiple animations and drawings that explain this phenomenon, it is sometimes difficult to convince students of this fact. So, based on the phenomenon of refraction, we can do a practice that allows students to experience the phenomenon for themselves.
The practice is based on the phenomenon of refraction of light waves as they pass through different substances. To start the practice it is necessary to put the students in a circle arount a table. A coin and a crystallizer are needed. Under the crystallizer a coin is placed and all students can see it. The crystallizer is slowly filled with water and there comes a time when the currency is not seen because the light beam has been deflected by the glass, water and air, not being able to reach the eye of the student. At that time students come near the table and if they look at the crystallizer perpendicular (from the top) they can clearly see the currency, which had previously disappeared from their view.
From this experience students better understand the phenomenon of refraction and understand that when an earthquake occurs there are shaded areas for seismic waves on the planet.