# Is it possible to create a magnetic field which can be seen?

• I
Hello,

I am wondering if one can create a magnetic field which can be seen by a human eye? I have learnt that light is nothing else but electromagnetic field with a wavelength between 400-800 nm. Colours correspond to different wavelength within the above spectrum. So isn't it theoretically possible to produce a magnetic field with lets say wavelength of 500 nm? Wouldn't that imply that such a magnetic field would appear to us in some colour?

Best wishes

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lekh2003
Gold Member
Hello,

I am wondering if one can create a magnetic field which can be seen by a human eye? I have learnt that light is nothing else but electromagnetic field with has a wavelength between 400-800 nm. Colours correspond to different wavelength within the above spectrum. So isn't it theoretically possible to produce a magnetic field with lets say wavelength of 500 nm?

Best wishes
You must learn some more introductory physics. Magnetism is another force altogether. You can't possibly be able to see it. It doesn't have a wavelength like you think.

Thank you for your answer. But a magnetic field is a solution of the wave equation, so in my understanding it should be called a "wave". Doesn't have any wave also a wavelength?

lekh2003
Gold Member
Thank you for your answer. But a magnetic field is a solution of the wave equation, so in my understanding it should be called a "wave". Doesn't have any wave also a wavelength?
But I don't think you can create a wavelength of magnetism. All matter and electromagnetic radiation has waves, but not magnetism. Electromagnetic radiation is only induced from magnetism when there is magnetic flux. This wavelength is far from visible light. Let me remind you that electromagnetic waves span a massive range of lengths.

blue_leaf77
Homework Helper
So isn't it theoretically possible to produce a magnetic field with lets say wavelength of 500 nm?
When you look at a green colored object you most likely have seen a 500 nm wavelength magnetic field along with the electric field with the same wavelength. If however you want to produce a stand alone space and time varying magnetic field unaccompanied by electric field, it's theoretically not possible - Maxwell's equations forbid you to do that.

HastiM and lekh2003
@blue_leaf77: Thank you very much for your answer!!! I had not thought about the problem from that point of view! I must admit that I do not understand your last comment completely. Could you please explain why Maxwell's equations do forbid such an unaccompanied magnetic field?

Drakkith
Staff Emeritus
I have learnt that light is nothing else but electromagnetic field with a wavelength between 400-800 nm.
Not quite. See more below.

So isn't it theoretically possible to produce a magnetic field with lets say wavelength of 500 nm? Wouldn't that imply that such a magnetic field would appear to us in some colour?
I think there's some confusion with different concepts here. First and foremost, light is an electromagnetic wave. An EM wave is a propagating disturbance of the EM field, it is not the field itself.

Second, a field is a mathematical way of modeling something. The details are a bit complicated, but basically the EM field is a field that we use to model the electromagnetic interactions between particles in such a way that doesn't require us to place a test charge at every location that we might be interested in and then doing a calculation. This field is not capable of having a wavelength. Wavelength is a term that just doesn't apply to the field itself since the field is not a wave.

Could you please explain why Maxwell's equations do forbid such an unaccompanied magnetic field?
Our experiments and observations have shown that a varying magnetic field is always accompanied by a varying electric field, and vice-versa. Not only that, but we've also discovered that the electric and magnetic fields are just slightly different versions of the same thing. That "thing" is the electromagnetic field. You might set up a magnetic field in your lab, but if I come blazing through your lab at a super high velocity, I'll actually see your magnetic field as an electric field instead.

This observation that the electric and magnetic fields are linked to each other leads to our equations forbidding a varying magnetic field without an accompanying electric field.

HastiM, davenn and anorlunda
Staff Emeritus
2019 Award
You must learn some more introductory physics.
Pot. Kettle. Just sayin'.

There's a lot of misinformation in this thread. If I have a magnetic field pulsed at an optical frequency (however I manage to do that), it absolutely will produce visible light. I'm not sure where the "no electric field" part came in, but the oscillating magnetic field will itself produce an oscillating electric field. You won't have one without the other.

davenn
sophiecentaur