A nanometre is one-billionth of a metre, and 700 nanometres falls within the visible light spectrum. Specifically, it corresponds to the colour red, which is at the longer wavelength end of visible light. In practical terms, 700 nanometres is significant in various fields, including optics and photography. It helps in understanding how light interacts with materials and is crucial for technologies like LEDs and lasers that emit light at specific wavelengths.