Using IR Sensor to sense movement? I was wondering if I could use a IR sensor with my Arduino to detect if someone is present in front of it. 

Like, the emitter should emit continuously and if the receiver drop connection it should do something.

Will this work fine? or the emitter wide angle and a human body in front of it wont drop the signal?
This will work fine. The easiest way to do this is using IR Sensor Module.



This will give you a digital output of whether there is someone in front of sensor or not. Use can use it as an Edge Trigger to detect Humans passing by.

You can buy one. They are both cheap and easily available.

Or you can create your own.