A plane electromagnetic wave of frequency 500 MHz is travelling in vacuum along y-direction. At a particular point in space and time, $\overrightarrow B = 8.0 \times 10-8 \widehat zT. The value of electric field at this point is :(speed of light = 3 \times 108 ms-1)\widehat x, \widehat y, \widehat z$ are unit vectors along x, y and z directions.