In the Young's double slit experiment $$n^{\text {th }}$$ bright for red coincides with $$(n+1)^{\text {th }}$$ bright for violet. Then the value of '$$n$$' is: (given: wave length of red light $$=6300^{\circ} \mathrm{A}$$ and wave length of violet $$=4200^{\circ} \mathrm{A}$$).

When light wave passes from a medium of refractive index '$$\mu$$' to another medium of refractive index '$$2 \mu$$' the phase change occurs to the light is :

The width of the fringes obtained in the Young's double slit experiment is $$2.6 \mathrm{~mm}$$ when light of wave length $$6000^{\circ} \mathrm{A}$$ is used. If the whole apparatus is immersed in a liquid of refractive index 1.3 the new fringe width will be :

In a single slit diffraction experiment, for slit width '$$\alpha$$' the width of the central maxima is '$$\beta$$'. If we double the slit width then the corresponding width of the central maxima will be: