What does particle mean to you? If an atom is a particle, than the statement is clearly not true (a wave does get absorbed when the particle size is smaller than that of the wavelength of the wave).

The question is not rather clear to me, I just try to provide a first guess:

If you think of the particle (say a small metallic needle) as of an antenna, it is tuned to some frequencies.  In a case of a small particle, these frequencies are rather higher than the incoming wave and there is poor absorption.

Nagbhusan,

A radio wave at medium wave range ( several hundred meters wavelength) gets absorbed by the antenna in the radio. So your observation is not true in general.

If you mean a particle like electron, then you have to redefine what you mean by absorption.

Regards,

Rajat

I think there is a confusion. It is known that as bold approximation one can say that maximum extinction of light is at the wavelength of the order of particle dimensions.