The basic concept of the de broglie waves that shows the dual nature of matter is explained here conceptually, aapko samajh aayega ki why he use this formula for wave and matter? and when any matter can show the dual nature? what is the condition for that?
As you know that light (EMwaves,electromagnetic field) exhibit both nature particle (photon) as well as waves(wave) can matter also show the dual nature? this was the greatness of this concept. watch the full video and see at what condition they show it and what is the meaning of wave packet/envelope is and their velocity?
You can see related videos
1. de Broglie Waves-Matter Waves and its Wavelength
2. Concept of Wave Packet, Phase Velocity & Group Velocity for de Broglie Waves