In young's double slit experiment, the \mathrm{n}^{\text{th }} maximum of wavelength \lambda_1 is at a distance of y_1 from the central maximum. When the wavelength of the source is changed to \lambda_2,\left(\frac{\mathrm{n}}{3}\right)^{\text{th }} maximum is at a distance of y_2 from its central maximum. The ratio \frac{y_1}{y_2} is