Honestly, I don’t know for sure. I’m pretty sure. Sure enough so that I believe it goes off, but I can’t prove it doesn’t instead stay on when the door closes.
The light is incandescent so it emits heat. When I open the door and the light is on (notice I didn’t say “turns on”, I can touch it with my bare hands, and its cold. If I hold the door open for a minute or so the light is definitely warm to the touch. Does that prove the light was off when the door was closed and only switched on when I opened the door? perhaps, but that isn’t real proof. Maybe the temperature inside is so cold that it counteracts the warmth generated by the lightbulb?
The light seems to last a long time. I mean, I’ve owned my current refrigerator for over 2 years and have never replaced the bulb. Remember its incandescent so I have to believe that if it were constantly on it would’ve burned out by now and need to be replaced. So does that prove that the light spends most of its time off? Not necessarily, again its more circumstantial proof.
How can I find out for sure if the light indeed turns off when I close the refrigerator door? The most definitive way to prove this is that I could drill a hole in the door. A hole large enough to look through and see – for certain – to prove beyond any doubt that the light indeed does turn off when the door closes.
The problem with that strategy is that it effectively renders my refrigerator useless. I proved the hypothesis, but I ruined my refrigerator… damn it!