What is the region of this wavelength (462 nm)?
Light with a wavelength of 462nm is in the visible light region (blue light visible by the human eye). 

For certain, your lecturer was wrong that the light is in the infrared region, this occurs at much higher wavelengths closer to 700nm. More possibly he meant to say ultraviolet, which occurs somewhere below 400nm (shorter wavelengths), though even this isn't technically correct. 

The Wikipedia article gives a fairly good overview of the various regions, along with a schematic describing where they come: