In biprism experiment, the fringe width is 0.6 mm . The distance between $6^{\text {th }}$ dark fringe and $8^{\text {th }}$ bright fringe on the same side of central bright fringe is

In Young's double slit experiment, 'I' is the minimum intensity and ' $I_1$ ' is the intensity at a point where the path difference is $\frac{\lambda}{4}$ where ' $\lambda$ ' is the wavelength of light used. The ratio $I_1 \mathrm{I}_1$ is (Intensities of the two interfering waves are same) $\left(\cos 0^{\circ}=1, \cos 90^{\circ}=0\right)$

Considering interference between two sources of intensities ' I ' and ' 4 I ', the intensity at a point where the phase difference is $\pi$ is $(\cos \pi=-1)$

The phase difference between two waves giving rise to dark fringe in Young's double slit experiment is ( n is the integer)