system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: IF I use a laser thermometer to take a temperature through glass, does it give me the temperature of the glass or the object past it?
gpt
The laser isn't taking the temperature, it's just there for aiming. The device is measuring the incoming infrared radiation emitted from the object in the direction of the laser. Just because glass is transparent doesn't mean it doesn't emit infrared. So you are taking the temperature of the glass. 


That said, infrared can somewhat go through glass, not as easily as visible though. So a really hot object behind the glass that the laser is pointing at would have some of it's infrared radiation go through the glass and fool the thermometer into saying the glass is hotter than it is. It's also somewhat reflective to infrared too, so if you have a really hot object in the direction of the laser reflection off the glass that would also throw off the temperature reading of the glass.