Question

How large would the electric field need to be to split the mj -/+1 626.6 nm line of neon?

Answer 1

I feel that it is due to the wave-particle duality, where photons can exist as both a particle and a wave. In this case then, a single photon in itself also produces a wave (you can check out Young's experiment on proving wave-particle duality, where even a single electron proved to have created a wave). Hence, this electromagnetic wave induces an electric field, and therefore even with a single photon, an electric field can still be created.

Answer 2

Here is your answer

I feel that it is due to the wave-particle duality, where photons can exist as both a particle and a wave. In this case then, a single photon in itself also produces a wave (you can check out Young's experiment on proving wave-particle duality, where even a single electron proved to have created a wave). Hence, this electromagnetic wave induces an electric field, and therefore even with a single photon, an electric field can still be created.