Waves of energy

[Prometheus]

Just having some difficulty visualising how electromagnetic waves transmit energy. It is easy enough to visualise when waves propagate in a medium -the kinetic energy of sound waves for instance. But light does not need a medium to propagate. Is the wave itself energy, though i'm not even sure what that means? Is it the disturbance in the electromagnetic field which carries the energy? This i can visualise but then i'm missing something else as it would then seem that light is propagating through the electromagnetic field - contrary to what i have learnt.

[studiot]

When light is regarded as an electromagnetic wave it creates its own field. It is not a disturbance in someone elses' field.

 

This is how it can propagate through otherwise empty space.

 

In fact it is more complicated because it creates two fields. An electric one and a magnetic one.

 

The electric field is not constant but waxes and wanes in a cyclic manner.

 

Any changing electric field generates a magnetic field at right angles to itself.

 

This magnetic field changes cyclically because the electric field changes cyclically.

 

In turn, a changing magnetic field generates an electric field at right angles to itself.

 

This electric field changes cyclically because the magnetic field changes cyclically.

 

 

So the electric field generates the magnetic field, which generates an electric field which generates a magnetic field.............

 

and so the wave progresses with energy being swopped back and fore between electric and magnetic as it is passed down the line.

 

Here are lots of pictures showing this.

 

https://www.google.co.uk/search?tbm=isch&hl=en-GB&source=hp&biw=&bih=&q=electromagnetic+waves&gbv=2&oq=elctromagn&gs_l=img.1.2.0i10l10.2390.4297.0.8812.10.10.0.0.0.0.172.1173.0j10.10.0....0...1ac.1.34.img..0.10.1173.nrwAKu8N_fU

Edited March 15, 2014 by studiot

[Enthalpy]

Electric and magnetic fields store energy in vacuum. This is the case as well for a capacitor as for a propagating wave.

This propagating energy subsists when the source has disappeared. Many remote stars and galaxies that we observe are already extinct.

 

Whether it's vacuum or the field that stores energy... I fear this question has no answer. How should we measure a difference?

 

Yes, electric and magnetic fields are mysterious, in the sense that we have no direct feeling for them. We have equations to make accurate predictions (...sometimes! When not fooled, which happens often with electromagnetism), and we can try to build mental images like streams, but that's all more or less. Maybe some birds, who have a sense for magnetic field, have a natural comprehension for it, but we don't.

[swansont]

 

Whether it's vacuum or the field that stores energy... I fear this question has no answer. How should we measure a difference?

 

 

We can measure if there is a field present.

 

The model we have says the energy is stored in the field.

[arc]

So the wave is the "conservation of energy" doing the thing it does to the light or magnetic energy?

[swansont]

Energy is a property of the electromagnetic wave, as is linear momentum and angular momentum.

[Prometheus]

When light is regarded as an electromagnetic wave it creates its own field. It is not a disturbance in someone elses' field.

 

That's what i was missing, thanks (still plenty more though).

[studiot]

 

So the wave is the "conservation of energy" doing the thing it does to the light or magnetic energy?

 

 

 

Energy is a property of the electromagnetic wave, as is linear momentum and angular momentum

 

Swansont's answer give a clue as to why a wave travelling in one direction can meet another wave travelling in a different direction, the two waves have a conflab at their meeting point, and then pass through each other each going their separate ways as if they had never encountered each other.

 

This is entirely different behaviour from that of solid particles.

 

Energy does not preserve direction, momentum does.