That is incorrect. If a electromagnetic wave can penetrate stuff is not a linear function. E.g. visible light can not penetrate through a body but higher frequency such as x-rays can, however in the microwave spectrum it's different. Somebody said that short waves are really low frequency and can therefore go around the world, however they can really only do that because they cannot penetrate the ionosphere and are reflected back. In certain parts of the EM spectrum you can make certain assumption.