I am new here so I will start with a warming up question :) My question is very trivial here we go: In double slit experiment when shooting one photon at a time, we get interference pattern. Then when we put a sensor at one of the slits the interference pattern disappears because we now know which path the photon took. Now with same setup, if we switched from shooting single photons, to full source of light. In this case the sensor will register a swarm of photons passing by. So in this case the measurement will become meaningless and the which path information will become obscure because we cannot tell which photon took which path, consequently the interference pattern shall come back again.