A prism of refractive index $n_1$ and another prism of refractive index $n_2$ are stuck together (as shown in the figure). $n_1$ and $n_2$ depend on $\lambda ,$ the wavelength of light, according to the relation $n_1=1.2+\frac{10.8\times {10}^{-14}}{{\lambda }^2}$ and $n_2=1.45+\frac{1.8\times {10}^{-14}}{{\lambda }^2}$ 

The wavelength for which rays incident at any angle on the interface $BC$ pass through without bending at that interface will be ____ $\mathrm{nm}.$

Hence, the correct answer is 600.