Values IDW interpolation do not decrease

Wouter

I use IDW interpolation to see how light intensity is spreading across an area. When I perform IDW the values of the intensity decrease but after a certain distance the values stop to decrease. Then all the values are the same but I would expect them to decrease until the intensity reaches the value of 0. Is IDW incapable of doing this? 

 

JayantaPoddar

What is the range of values represented by the points?

According to IDW (Spatial Analyst)—ArcGIS Pro | Documentation, "The output value for a cell using inverse distance weighting (IDW) is limited to the range of the values used to interpolate. Because IDW is a weighted distance average, the average cannot be greater than the highest or less than the lowest input..."