A plane electromagnetic wave is propagating along the direction ${{\widehat i + \widehat j} \over {\sqrt 2 }}$ , with its polarization along the direction $\widehat k$ . The correct form of the magnetic field of the wave would be (here B₀ is an appropriate constant) :

1. A $${B_0}{{\widehat i - \widehat j} \over {\sqrt 2 }}\cos \left( {\omega t - k{{\widehat i + \widehat j} \over {\sqrt 2 }}} \right)$$ Correct answer
2. B $${B_0}{{\widehat i + \widehat j} \over {\sqrt 2 }}\cos \left( {\omega t - k{{\widehat i + \widehat j} \over {\sqrt 2 }}} \right)$$
3. C $${B_0}{{\widehat j - \widehat i} \over {\sqrt 2 }}\cos \left( {\omega t + k{{\widehat i + \widehat j} \over {\sqrt 2 }}} \right)$$
4. D $${B_0}\widehat k\cos \left( {\omega t - k{{\widehat i + \widehat j} \over {\sqrt 2 }}} \right)$$