In Young's double slit experiment, the resultant intensity of light at a point on the screen is 'I' when the path difference is $\lambda^{\prime}$ '. When the path difference is $\frac{\lambda}{4}$, the intensity at a point will be $\left(\lambda=\right.$ wavelength of light, $\cos 180^{\circ}=-1, \cos 45^{\circ}=\frac{1}{\sqrt{2}}$ )