Phase of Time Varying E-M Fields

[ElectricKitchen]

Are the E and M components of an E-M wave (at a given frequency) necessarily in phase in free space? A conductor? A dielectric material?

 

[Dale]

We had a recent discussion of this here
https://www.physicsforums.com/threads/out-of-phase-em-wave.849947/#post-5331597

 

[ElectricKitchen]

Thanks. I must have missed it.