CBSE 2026 · Region 2 · Set 2 · Q7 · 1 mark

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?

CBSE Class 12 Physics past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.