The expression of magnetic fields associated with four electromagnetic waves are given below: I. B_1=(4 × 10^-6 T ) sin [0.7 × 10^3 x+1.4 × 10^11 t ]…

The expression of magnetic fields associated with four electromagnetic waves are given below : I. $\displaystyle \mathrm{B}_{1}=\left(4 \times 10^{-6} \mathrm{~T}\right) \sin \left[0.7 \times 10^{3} x+1.4 \times 10^{11} \mathrm{t}\right]$ II. $\displaystyle \mathrm{B}_{2}=\left(2 \times 10^{-7} \mathrm{~T}\right) \sin \left[0.6 \times 10^{3} x+1.5 \times 10^{11} \mathrm{t}\right]$ III. $\displaystyle \mathrm{B}_{3}=\left(3 \times 10^{-5} \mathrm{~T}\right) \sin \left[0.5 \times 10^{3} x+1.5 \times 10^{11} \mathrm{t}\right]$ IV. $\displaystyle \mathrm{B}_{4}=\left(5 \times 10^{-4} \mathrm{~T}\right) \sin \left[0.2 \times 10^{4} x+4.8 \times 10^{11} \mathrm{t}\right]$ Which wave is travelling in free space?