Two different wavelengths of monochromatic light are projected through the same double slit. First a 490 nm light is projected and it forms a diffraction pattern where the second-order minimum is located 12.5 mm from the central bright spot on a screen 1.4 m from the slits. When the second light is projected through the slits the second-order maximum is located 12.5 mm from the central bright spot on the screen. What's the unknown wavelength?
? nm