The extent of polarity (or polarization) of a molecule is expressed in terms of dipole moment which is defined as follows:

The dipole moment of a polar diatomic molecule is the product of the charge on each end of the molecule and the average*distance between the charge on each end of the molecule and the average*distance between the centers of their nuclei i.e. the bond length.
 

In general, for a polar diatomic molecule AB in which atom B is more electronegative than A, if + q is the charge  on the end A-q on the end B of the molecule** and d is the average distance between the centers of their nuclei, then the dipole moment of the molecule AB is given by
                                       
Obviously if the molecule is non-polar , q = 0 and hence

For more help in Dipole Moment of  a diatomic molecule please click the button below to submit your homework assignment.