Young's double slit experiment is carried out by using green, red and blue light, one colour at a time. The fringe widths recorded are $$\beta$$_G, $$\beta$$_R and $$\beta$$_B, respectively. Then,

A light ray travelling in glass medium is incident on glass-air interface at an angle of incidence $$\theta$$. The reflected (R) and transmitted (T) intensities, both as function of $$\theta$$, are plotted. The correct sketch is

Column I shows four situations of standard Young's double slit arrangement with the screen placed far away from the slits S$$_1$$ and S$$_2$$. In each of these cases, S$$_1$$P$$_0$$ = S$$_2$$P$$_0$$, S$$_1$$P$$_1$$ $$-$$ S$$_2$$P$$_1$$ = $$\lambda/4$$ and S$$_1$$P$$_2$$ $$-$$ S$$_2$$P$$_2$$ = $$\lambda/3$$, where $$\lambda$$ is the wavelength of the light used. In the cases B, C and D, a transparent sheet of refractive index $$\mu$$ and thickness t is pasted on slit S$$_2$$. The thickness of the sheets are different in different cases. The phase difference between the light waves reaching a point P on the screen from the two slits is denoted by $$\delta$$(P) and the intensity by I(P). Match each situation given in Column I with the statement(s) in Column II valid for that situation:

	Column I		Column II
(A)		(P)	$$\delta ({P_0}) = 0$$
(B)	$$(\mu-1)t=\lambda/4$$	(Q)	$$\delta ({P_1}) = 0$$
(C)	$$(\mu-1)t=\lambda/2$$	(R)	$$I({P_1}) = 0$$
(D)	$$(\mu-1)t=3\lambda/4$$	(S)	$$I({P_0}) > I({P_1})$$
		(T)	$$I({P_2}) > I({P_1})$$

The figure shows surface XY separating two transparent media, medium -1 and medium -2 . The lines ab and cd represent wavefronts of a light wave traveling in medium -1 and incident on X Y. The lines ef and gh represent wavefronts of the light wave in medium -2 after refraction.

Speed of the light is