A beam of polychromatic light passes through a thin prism of prism angle $$6^\circ$$. The refractive index of the material of the prism varies with wavelength $$(\lambda)$$ as $$n(\lambda)=\alpha\lambda+\dfrac{\beta}{\lambda^2}$$, where $$\alpha=3\,\mu\mathrm{m^{-1}}$$ and $$\beta=0.096\,\mu\mathrm{m^2}$$. If $$\lambda_{\min}$$ is the wavelength at which the angle of minimum deviation $$D_m$$ is smallest, then the correct value of $$D_m$$ at $$\lambda_{\min}$$ is