In a Young's double slit experiment, the slits are separated by \( 0.3 \, \text{mm} \) and the screen is \( 1.5 \, \text{m} \) away from the plane of slits. Distance between fourth bright fringes on both sides of central bright fringe is \( 2.4 \, \text{cm} \). The frequency of light used is ______ \( \times 10^{14} \, \text{Hz} \) .
