Proving E and B are orthogonal

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In summary, the conversation discusses the relationship between the electric and magnetic fields, with one participant questioning if the del cross something also follows the rule that both components are orthogonal to the result. The other participant explains that while this is true for certain solutions to Maxwell's equations, it is not a universal rule. The conversation then shifts to discussing vacuum plane wave solutions and the conditions for light to occur. It is concluded that E.B=0 is necessary for light, but not sufficient.
  • #1
Kidphysics
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Homework Statement



E . B =0

Homework Equations



∇xE=B

The Attempt at a Solution



I know AxB=C implies both A and B are orthogonal to C but does the same thing ring true for the Del cross something? In any case, is there a nice simple proof for the problem stated? This is not HW by the way but seems to be a bit homeworish
 
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  • #2
You're going to have to be way more detailed. I'm assuming E and B are the electric and magnetic field respectively. If so, then in general they are not orthogonal. For special solutions to Maxwell's equations they can be orthogonal, such as for vacuum radiation fields, but it is certainly not true in full generality.
 
  • #3
WannabeNewton said:
You're going to have to be way more detailed. I'm assuming ##E## and ##B## are the electric and magnetic field respectively. If so, then in general they are not orthogonal. For special solutions to Maxwell's equations they can be orthogonal, such as for vacuum radiation fields, but it is certainly not true in full generality.

ah, for it to be light must they be orthogonal?
 
  • #4
Have you seen vacuum plane wave solutions to Maxwell's equations before?
 
  • #5
WannabeNewton said:
Have you seen vacuum plane wave solutions to Maxwell's equations before?

yes it says this must be the case. For light. I guess this means E.B=0 for light but it is not necessary for them to be orthogonal, but this does not mean it is light if the first condition is not met?
 

1. What does it mean for E and B to be orthogonal?

Orthogonal means that two vectors are perpendicular to each other. In the context of electromagnetism, it means that the electric and magnetic fields are at right angles to each other.

2. Why is it important to prove that E and B are orthogonal?

Proving that E and B are orthogonal is important because it is a fundamental principle in electromagnetism. It helps us understand the relationship between electric and magnetic fields and how they interact with each other.

3. How is the orthogonality of E and B demonstrated experimentally?

The orthogonality of E and B can be demonstrated experimentally by using a device called a Faraday cage. This cage blocks external electric fields and allows for the measurement of the magnetic field perpendicular to the electric field inside the cage.

4. Are E and B always perfectly orthogonal?

In theory, E and B should always be perfectly orthogonal to each other. However, in practical situations, there may be slight deviations due to factors such as the geometry of the setup or the presence of other electromagnetic fields.

5. How does the orthogonality of E and B relate to Maxwell's equations?

Maxwell's equations, which describe the behavior of electric and magnetic fields, also show that E and B are orthogonal to each other. This relationship is known as the "curl-free" condition, which states that the curl of the electric field is equal to the negative of the time rate of change of the magnetic field, and vice versa.

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