In the final room, the path for the mirror lights only became visible by using a UV-light. This is very common in escape rooms, but because of the physical principles that underline this phenomenon, this escape room too makes use of it. Invisible ink works by excitation and photon emission by electrons. In fluorescence the wavelength of the emitted light is longer than of the absorbed wavelength. UV-light has has a wave length that is just too short to be in the visible range and therefore impossible to see. It is, however, very energetic light and is also what causes sunburns. When it interacts with materials that display fluorescence, the electrons emit a longer wavelength that puts it on the visible spectrum. Moreover, different materials interact in different ways with UV-light. In effect, this means that the electrons are raised to a different excited energy and therefore, when they ae released, various colours can be achieved. Hence, the chalk in the final room was visible in a specific colour.
