The discussion revolves around the application of the concept of wavelength to electromagnetic fields, particularly in the context of de Broglie wavelength. Participants explore the criteria that determine whether something can be said to have a wavelength, especially when considering entities that possess momentum but not mass.
The discussion is active, with participants raising questions about the nature of wavelengths in different contexts. Some guidance has been offered regarding the limitations of applying the concept of wavelength to DC fields, particularly in relation to boundary conditions and the nature of wave functions.
There is an emphasis on the distinction between free propagation and scenarios involving boundaries, which complicates the application of wavelength concepts. The original poster and others express confusion regarding the implications of these conditions on the definition of wavelength.
ascky said:Are there other criteria, other than whether something has mass or momentum, that must be fufilled before talking about something having a wavelength?
The description in terms of de Broglie wavelength is - you might imagine - rather crude. In reality, you have to solve a mathematical problem to find an entire wave function, and the concept of wavelength only applies to very special kinds of solutions, namely sine waves. This is not going to be always possible (in fact, it is only possible in empty space, when the things are propagating freely, and even then not all solutions have to take on that aspect).ascky said:So how would one go about calculating the wavelength of, say, a dc electric field?