Wave Optics

In Young's double slit experiment the intensities at two points, for the path difference \(\frac{\lambda}{4}\) and \(\frac{\lambda}{3}\) (\(\lambda=\) wavelength of light used) are \(I_1\) and \(I_2\) respectively. If \(\mathrm{I}_0\) denotes the intensity produced by each one of the individual slits then \(\frac{\mathrm{I}_1+\mathrm{I}_2}{\mathrm{I}_0}\) is equal to \(\left(\cos 60^{\circ}=0.5, \cos 45^{\circ}=\frac{1}{\sqrt{2}}\right)\)