Compatible with De Broglie's description

[Miyown Meeks 2F]

Can someone please explain how you can tell if a wave is compatible with De Broglie's description by looking at it, I'm a little confused.

[Sai Alapati 3K]

You can tell that a wave is compatible if it can be cut anywhere and then rejoined and still be continuous. In other words, the wave has to have a whole number of wavelengths and it has to be standing which means that there is only one frequency and wavelength for the entire wave.