A uniform plane wave with electric field $E⃗(x)=A_y â_y e^{-j\frac{2πx}{3}} V/m$ is travelling in the air (relative permittivity, $ε_r=1$ and relative permeability, $μ_r=1$) in the +x direction ($A_y$ is a positive constant, $â_y$ is the unit vector along the y-axis). It is incident normally on an ideal electric conductor (conductivity, σ=∞) at x=0.
The position of the first null of the total magnetic field in the air (measured from x=0, in metres) is