Please look at the attachments below. I shall use the word "modulation" instead of "amplitude modulation" since I've been taught about AM only. So, my question is, in the first image (that I've attached), the messenger wave (which is modulated with the high frequency carrier wave) as well as the modulated wave, both are shown to be varying with time - and their phase is also changing (just like ALTERNATING CURRENT). So, this is the wave which is transmitted. But, in the second image - which shows the fate of the transmitted wave after being received by the receiver antenna- the output wave is shown to be varying with time - but its phase is not changing (i.e. The variations are limited to one quadrant only - above the axis only ) - just like time varying DC. So, 1) Can the arrangement be used to convert AC into DC? 2) Is the change acceptable? I mean - the input wave's phase was changing - but it is not so with the output wave. So, will it affect the efficiency? Like- in the case of a voice signal?