Find an expression for a magnetic field from a given electric field

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SUMMARY

The discussion focuses on deriving an expression for the magnetic field from a given electric field, referencing Zangwill's "Modern Electrodynamics." A key point is the correct representation of the electric field components, specifically the \(\mathbf{x}_1\) component, which should be expressed as \(\epsilon_1 e^{i(k_1x_1 + k_2x_2 + k_3x_3 - \omega t)}\). The curl of the electric field can be computed using the chain rule, leading to the formula \(\nabla \times (\mathbf{c}f(\zeta(\mathbf{x}))) = f'(\zeta) ((\nabla \zeta) \times \mathbf{c})\).

PREREQUISITES
  • Understanding of vector calculus, specifically curl operations.
  • Familiarity with electromagnetic theory as outlined in Zangwill's "Modern Electrodynamics."
  • Knowledge of complex exponentials and their application in physics.
  • Ability to work with scalar and vector fields in three-dimensional space.
NEXT STEPS
  • Study the application of the curl operator in electromagnetic fields.
  • Explore the implications of the chain rule in vector calculus.
  • Review the derivation of Maxwell's equations from electric and magnetic field relationships.
  • Investigate the role of complex numbers in electromagnetic wave propagation.
USEFUL FOR

This discussion is beneficial for physics students, researchers in electromagnetism, and educators seeking to deepen their understanding of the relationship between electric and magnetic fields.

TechieDork
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Homework Statement
Find an expression for a magnetic field B(X,t) from a given electric field in a monochromatic plane wave solution E(X,t) using Maxwell's equations.
Relevant Equations
E(X,t) = εe^i(kX-ωt) , X = (x1,x2,x3) , k = (kx1,kx2,kx3) , ω = c|k| , k·ε = 0
ε is a complex vector
Here this is my attempt :

SSZ.jpg


Reference Textbook : Zangwill's Modern Electrodynamics

I stuck at the last step , I really have no idea what to do next.
 
Last edited:
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You have not split \mathbf{E} into its components correctly. The \mathbf{x}_1 component of \mathbf{E} should be \epsilon_1 e^{i(\mathbf{k}\cdot \mathbf{x} - \omega t)} = \epsilon_1 e^{i(k_1x_1 + k_2x_2+k_3x_3 - \omega t)}, etc.

But you don't need to split this into components.

The electric field depends on \mathbf{x} only through a constant vector times a scalar function of the dot product, so its curl is computed most easily by the chain rule: <br /> \nabla \times (\mathbf{c}f(\zeta(\mathbf{x}))) = f&#039;(\zeta) ((\nabla \zeta) \times \mathbf{c}).
 
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