  There has been an intense debate on the question as to whether a quanton,
passing through a double-slit, experiences a 'momentum kick' due to the act of
which-way detection. There have been conflicting points of view on this issue
over many decades. This issue is addressed here in the general setting where
the which-way detection may be imperfect. It is shown here that the loss of
interference may still be interpreted as arising out of tiny momentum kicks
which the quanton appears to receive, irrespective of the nature of the
which-way detector. Interestingly, the magnitude of the random momentum kicks
is always h/2d, d being the slit separation, irrespective of how perfect or
imperfect the which-way detection is. This is contrary to what has been
suggested in the earlier literature. The imperfection of which-way detection
decides how frequent are the momentum kicks. It has been shown earlier that for
perfect which-way detection, the quanton receives a momentum kick fifty percent
of the time. Here it is shown that for imperfect which-way detection, the
quanton receives momentum kicks of the same magnitude, but less often. A
precise relation between the frequency of kicks and the visibility of
interference is found here.
