A plane electromagnetic wave in vacuum has electric field E = (30 V ,m^ -1 ) (ky - t)

PHYSICS · Subjective · Fermi University Physics · Electricity, Magnetism & Electromagnetism · Optics & Photonics · Polarisation and anisotropic media

Electricity, Magnetism and Electromagnetism, Ch Plane electromagnetic waves: polarisation, energy flux and radiation pressure

Problem

A plane electromagnetic wave in vacuum has electric field E=(30 V m−1)cos⁡(ky−ωt) z^,\mathbf{E} = (30\ \mathrm{V\,m^{-1}})\cos(ky - \omega t)\,\hat{\mathbf{z}}, with ω=ck\omega = ck and c=3.00×108 m s−1c = 3.00\times10^{8}\ \mathrm{m\,s^{-1}}. Exactly one of the following statements is correct. Choose it. (a) The wave is polarised along xx, because polarisation names the direction of the magnetic field, and B\mathbf{B} lies along xx. (b) The wave is polarised along zz; B\mathbf{B} lies along xx with amplitude E0/c=1.0×10−7 TE_0/c = 1.0\times10^{-7}\ \mathrm{T}, reaching its peaks at the same places and instants as E\mathbf{E}. (c) The wave is polarised along yy, since the polarisation is the direction in which the wave travels. (d) The wave is polarised along zz; B\mathbf{B} lies along xx with amplitude E0/c=1.0×10−7 TE_0/c = 1.0\times10^{-7}\ \mathrm{T}, but a quarter of a period behind E\mathbf{E}, as the two energies are in an LCLC circuit. (e) The wave is polarised along zz, and B\mathbf{B} also lies along zz, parallel to E\mathbf{E}.

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