An electron of mass m with an initial velocity \(\vec{v}\,=v_0\hat{i} \left( v_0\,>\,0 \right)\) enters an electric field \(\vec{E}\,=\,-\vec{E}_0 \hat{i} \left ( E_0 \,=\, constant\, >\, 0 \right )\) at t = 0. If \(λ_0\) is its de-Broglie wavelength initially, then its de-Broglie wavelength at time t is