This principle states that it is impossible to measure simultaneously the position and momentum of a small particle with absolute accuracy or certainty. If an attempt is made to measure any one of these two quantities with higher accuracy, then the other becomes less accurate. The product of uncertainty in the position and uncertainty in momentum is always constant and is equal to or greater than h/4p i.e.

Δx. Δp = h/4π

Where,

h is the Planks constant

Δx is the uncertainty in position

Δp is the uncertainty in momentum