In a Young's double slit experiment, the slits are separated by \(0.28\,\text{mm}\) and the screen is placed \(1.4\,\text{m}\) away from the slits. The distance between the central bright fringe and the \(4^{\text{th}}\) order bright fringe is measured to be \(1.2\,\text{cm}\). The wavelength of light used in this experiment is