Red light visible on my iPhone

It could happen through some circumstances that you'll be able to see IR light. For example:

• Some materials in your environment use dyes or fluorescence and when IR light hits such material, it could make the light visible
• If you're looking at your iPhone through a reflection or through another device, like a camera or other iPhone with camera, it could reflect the IR light and make it visible.
• Some variations in eye sensitivity, people may be more sensitive to the lower end of the visible light spectrum, so they could potentially see what other cannot.

Because the IR LED produces a small amount of light in the spectrum visible to humans, it is not 100% infrared light.