# Over what frequency range are Maxwell's equations valid?

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1. May 2, 2016

### MathPi

1. The problem statement, all variables and given/known data
I am studying for an Optics exam and in one of the practise tests is the following question: "Over what frequency range are Maxwell's equations valid?"

2. Relevant equations
Maxwell's Equations

3. The attempt at a solution
I've searched through my Griffiths Intro to electrodynamics, and all over Google, but came out short. Any leads would be appreciated.

2. May 2, 2016

### Staff: Mentor

Do you see any frequency dependent terms in Maxwell's Equations? Are you familiar with how to work with differential equations like the linked system of Maxwell's Equations?

3. May 2, 2016

### MathPi

I should add that this is not homework for a class that I am taking, nor am I receiving any marks for answering this question.
Yes I am familiar with solving DEs (I have a math degree). I am also familiar with Maxwells equations (I also have a physics degree). The question is literally as I have posted it - my best guess is that the these laws are not good at the quantum level and QED must be used (I am not too good at QED, I only took one course in subatomic physics).

I should add that this is not a homework question for a course I am taking. Nor am I receiving any marks for answering this.

4. May 2, 2016

5. May 2, 2016

### MathPi

It's just a guess - trying to come to an answer through discussion. Any constructive input is appreciated :)

6. May 2, 2016

### Staff: Mentor

I think you are over-thinking it.
What level is this question anyway. From your OP it sounded like it was at a pretty basic level:
Opticians don't do much with QM.

OTOH, if this is for a Quantum Optics class, there may be a different answer, I suppose.

7. May 2, 2016

### MathPi

Ah I should have specified the level. The exam is for an undergraduate optics at an advanced EM level (maybe 4th year physics).

8. May 2, 2016

### MathPi

Even if I am overthinking it there are only two possibilities: either Maxwells equations are valid for all frequencies, or they are not. If not, what are the ranges and why?

9. May 2, 2016

### Staff: Mentor

So QED may be involved? i'm not familiar with any frequency limitations of Maxwell's Equations, but are they modified for QED? That's kind of a different question.

10. May 2, 2016

### MathPi

I doubt QED is involved - that's too advanced for this course. Like I said it was just a guess - maybe not a good one! I cannot think of anything else besides that (trying to remember my subatomic physics course).

11. May 2, 2016

### Staff: Mentor

At least from my perspective, frequency limitations do not come into effect with the basic Maxwell Equations. Probably a trick question...

12. May 2, 2016

### MathPi

Yes you might be right. Perhaps I was hoping there was more to it. I'll take it as it is for now unless someone else has any thoughts. Thanks for your input!