If $\lambda_{\mathrm{Cu}}$ is the wavelength of $\mathrm{K}_\alpha \mathrm{X}$-ray line of copper (atomic number 29) and $\lambda_{\text {Mo }}$ is the wavelength of the $\mathrm{K}_\alpha \mathrm{X}$-ray line of molybdenum (atomic number 42), then the ratio $\lambda_{C \mu} / \lambda_{M \mathrm{M}}$ is close to