How does waves transfer energy forward I'm teaching a O-level physics student (grade 10th). We were talking about waves and she asked this question, how does waves transfer energy forward if the molecules just moving up and down? How does the energy stored in waves?
I struggle to explain this in a conceptual way. Can you please help me?
 A: The up and down movement of each individual point visualised only the fact that the wave does not transfer mass. However, the points are not independent, but coupled: If the position of a specific point $x_i$ is  $x_i - x_0$, where $x_0$ is the equilibrium position, the neighbouring points have similar positions.
The energy is transferred due to this coupling of the points. We can think of many pendula, which are coupled by springs. In this simplified picture the energy is stored as kinetic  and potential energy.
Please note that this idea is applicable to almost all waves except for the case of an electromagnetic wave: An electromagnetic wave does not consist of coupled particles with non-zero mass. Instead, the electromagnetic wave consists of electric and magnetic fields, which induce each another. Of course one could argue / try to motivate that the electric and magnetic fields are similar to the potential energy and that their changes in time are similar to the kinetic energy. However, in my opinion this picture probably generates confusion in the 10th grade.
