Sinosoidal curves representing waves

[Parbat]

we represent electromagnetic waves by sinosoidal curves.
magnitude of what changes sinosoidally?
or what does that represent?

 

[Upisoft]

we represent electromagnetic waves by sinosoidal curves.
magnitude of what changes sinosoidally?
or what does that represent?

y component of rotating unit vector in a plane. Edit: Rotating with constant angular speed, of course

 

[jtbell]

magnitude of what changes sinosoidally?

The magnitude of the electric field, and the magnitude of the magnetic field. (I assume you refer to a classical electromagnetic wave.)

We sometimes make a mathematical analogy with the x- or y- component of a rotating vector as upisoft noted.

 

[Parbat]

The magnitude of the electric field, and the magnitude of the magnetic field. (I assume you refer to a classical electromagnetic wave.)

how can magnetic & electric field become zero & again increase?how does that happen?