How is Charge conserved?

charge conservation, in physics, constancy of the total electric charge in the universe or in any specific chemical or nuclear reaction. The total charge in any closed system never changes, at least within the limits of the most precise observation. In classical terms, this law implies that the appearance of a given amount of positive charge in one part of a system is always accompanied by the appearance of an equal amount of negative charge somewhere else in the system; for example, when a plastic ruler is rubbed with a cloth, it becomes negatively charged and the cloth becomes positively charged by an equal amount.

wavelength divides in half and speed stays the same.