By relation, $\mathrm{c}=v \lambda \Rightarrow \lambda=\frac{\mathrm{c}}{v}$ $\lambda_1=\frac{3 \times 10^8}{7.5 \times 10^6}=40 \mathrm{~m}$ and $\lambda_2=\frac{3 \times 10^8}{12 \times 10^6}=25 \mathrm{~m}$ The corresponding wavelength band is $25 \mathrm{~m}$ to $40 \mathrm{~m}$.