Reddit reviews Hoya 58mm R-72 Infrared Filter

Yes, there are filters that block visible light and let IR through. You can buy one for a camera too (depending on the type of camera/lens), but most definitely not for $10 mentioned by another poster.

http://www.amazon.com/Hoya-58mm-RM-72-Infrared-Filter/dp/B0000AI1HP

If you are using a film camera, you will need special IR-sensitive film. If you are using digital, then you will have to have the UV + IR filter removed from over the sensor.

Source: I'm a photographer.

Here's the one I bought.

https://www.amazon.com/Hoya-58mm-R-72-Infrared-Filter/dp/B0000AI1HP/ref=sr_1_3?ie=UTF8&qid=1497204649&sr=8-3&keywords=hoya+r72+infrared+filter

Is this it?
http://www.amazon.com/Hoya-58mm-RM-72-Infrared-Filter/dp/B0000AI1HP

DSLRs have inbuilt filters that remove parts of the spectrum that you can't normally see (infrared, UV light etc.).

That said, some of the light still gets through to the sensor, just vastly reduced in brightness.

So all you need to do is block all light except for the infrared light and you'll be able to take infrared pictures; which is where an infrared filter comes into play.

Note that you'll want to do some searching, as some cameras are more sensitive to infrared than others. But it's likely you'll be looking at like 30 second exposures in the middle of the day.

then you pop one of these badboys on there to filter out the visible light spectrum
http://www.amazon.com/Hoya-58mm-RM-72-Infrared-Filter/dp/B0000AI1HP

and you get this
http://www.smashingmagazine.com/images/infrared-photography/fish.jpg

Visible light is brighter than infrared to your mobile phone camera but you can buy a filter to see just infrared

Here is the original source with some extra info