In a double slit experiment with monochromatic light, fringes are obtained on a screen placed at some distance from the plane of slits. If the screen is moved by \( 5 \times 10^{-2} \, \text{m} \) towards the slits, the change in fringe width is \( 3 \times 10^{-3} \, \text{cm} \). If the distance between the slits is \( 1 \, \text{mm} \), then the wavelength of the light will be _____ \( \text{nm} \).