# If light is linearly polarized, does it have some spatial extent?

If light (a photon) is linearly polarized, say vertically, does it have some vertical spatial extent (perhaps in amplitude)?

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It carries with it two fields: the electric field $\vec E$ and the magnetic field $\vec B$. These are both vector fields, in that they have vector values at every point in space. Off the trajectory of the photon, their value is the zero vector. At every point along the trajectory of the photon, however, you can associate a vector value for both the electric and the magnetic field. As a concrete example, take a linearly polarized photon traveling along the z-axis. The electric field oscillates in the direction of the x-axis, and the magnetic field oscillates in the direction of the y-axis. So light is often depicted in textbooks as having two oscillations around the axis of the trajectory, representing the electric and magnetic fields. The fields themselves are only present along the trajectory of the photon, though.