In Young's double slit experiment, light from two identical sources are superimposing on a screen. The path difference between the two lights reaching at a point on the screen is $\frac{7\lambda }{4}$. The ratio of intensity of fringe at this point with respect to the maximum intensity of the fringe is:

For light waves are represented by 

(i) $y=a_1\sin \omega t$

(ii) $y=a_2\sin \left(\omega t+\varphi \right)$

(iii) $y=a_1\sin 2\omega t$

(iv) $y=a_2\sin 2\left(\omega t+\varphi \right)$

Interference fringes may be observed due to superimposition of

In a Young's double slit experiment, the angular width of a fringe is $0.2°$ on a screen placed $1 \mathrm{m}$ away. The wavelength of light used is $600 \mathrm{nm}.$ The angular width of the fringe if the entire set up is immersed is a liquid of refractive index $1.33$ is,