The area of the circle at the end of the cone increases proportional to the square of the height (distance between sneezer and sneezee). Think that's probably the relevant bit.
So the amount of droplets in any given area at the end of the cone will decrease at a square of the distance? At 2 metres away, you'll get a quarter of the droplets you'd get at 1 metre away.
That's why rooms with high ceilings need proportionately bigger windows.
Still doesn't quite explain root 2 social distancing, sadly.