NEET Physics Properties of EM Waves MCQ Question

From the expression B_y = (2 × $10^{-7}$) T sin(0.5 × $10^3$ x + 1.5 × $10^{11}$ t), the wave number k is 0.5 × $10^3$ $m^{-1}$. The wavelength λ is given by λ = 2π/k = 2π/(0.5 × $10^3$) = 12.6 m.