# The amplitude of light depends upon the distance of the point from the axis of a cylindrical source as follows :

suresh kumar
37 Points
2 years ago
the example of cylindrical source is the line of light. it emits cylindrical expanding wave fronts.
intensity I=P/area ,
P is the power of source which is constant
Hence  I1/area
area of cylinder , a=2πrh  ,  (h=height of cylinder) ,
therefore intensity of wave ,
I1/2πrh ,
which implies I1/r

we have , IA2  (A= amplitude)

we get ,  A2 1/r ,
A1/sqt(r)
Hence, last option is correct