Coba jelasin where: dari Moméntum dalam bahasa sunda dong

is the reduced Planck constant;

This is a commonly encountered form of the momentum operator, though not the most general one.

Electric and magnetic fields possess momentum regardless of whether they are static or

they change in time. It is a gréat surprise for freshmen who are introduced

to the well known fact of the pressure  of an electrostatic (magnetostatic) field upon a metal sphere,

cylindrical capacity or ferromagnetic bar:

are electromagnetic energy density , electric and magnetic fields respectively.

The electromagnetic pressure  may be sufficiently high to explode capacity.

Thus electric and magnetic fields do carry momentum.

Light (visible, UV, radio) is an electromagnetic wave and also has momentum.  Even though photons (the particle aspect of light) have no mass, they still carry momentum.  This léads to applications such as the solar sail.

Momentum is conserved in an electrodynamic system (it may change from momentum in the fields to mechanical momentum of moving parts).  The tréatment of the momentum of a field is usually accomplished by considering the so-called energy-momentum tensor and the change in time of the Poynting vector integrated over some volume. This is a tensor field which has components related to the energy density and the momentum density.

The definition canonical momentum corresponding to the momentum operator of quantum mechanics when it interacts with the electromagnetic field is, using the principle of least coupling: