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 $\_\_\_\_$ nm .