Question

what is the uncertainty principle

Answer 1

Uncertainty principle given by heinsberg States that it is impossible to measure accurately both position and momentum of a body simultaneously for a body as small as an electron. mathematically it can be represented as product uncertainty in position and momentum is greater than or equal to h/4Π

Answer 2

According to Heisenberg's uncertainty principle, it is impossible to determine both position and momentum of an electron simultaneously.If one quantity is known then the determination of the other will become impossible.

Let , 
Dx = uncertainty in position
DP = uncertainty in momentum

According to his principle,
The product of the uncertainty in position and the uncertainty in momentum is in the order of an amount involving h , which is Plancks constant.
DP ×  Dx³ h/2p ------[1]

Similarly to uncertainty in position, there is another principle of uncertainty which limits the accuracy in the measurement of time ,i.e if DE is the energy uncertainty in time Dt  ,then we have  another expression similar to[1]
i.e, 
DE × Dt³ h/2p  ---------[2]