which one is an IR Emitter？ or all of those?

would an IR Emitter illuminate ?

 

IR is not visible to the naked eye.

 

It seems to me that the bottom one is IR diode.
And you can use a cellphone camera to see IR light.

 

IR is not visible to the naked eye.

so how to know the IR is working

 

It seems to me that the bottom one is IR diode.
And you can use a cellphone camera to see IR light.

how to see IR light by using a camera?

 

Connect the device to a voltage with a series resistor to limit the current to a few milliamps. If you have a 5 volt supply, a 2.2k resistor would be a good size.

Measure the voltage across the resistor to find the current (or use a milliammeter directly).

If the device is a detector, then you should see the current vary quite a lot when you shine a light on the device.

If the device is a transmitter, then just point an ordinary digital camera at it and look at the screen.

There's nothing special to do with the camera; all you do is when the camera display is showing what its lens is seeing, you just point the camera at the LED. My Canon digital camera shows IR LEDs glowing with kind of a dull bluish glow. It's not bright, but it's easily seen.

If little no current flows, then the device might be connected in the wrong polarity, so try it with the leads connected the other way.