A ray of light is incident at polarising angle $\theta$ on air-glass interface. If $\lambda_a$ and $\lambda_g$ are the wavelengths of light in air and glass respectively then

In biprism experiment, the maximum intensity is $I_0$. If the path difference between the two interfering waves is $\dfrac{\lambda}{3}$, then intensity at the point on the screen is
[$\sin 30^\circ = \cos 60^\circ = 0.5$, $\sin 60^\circ = \cos 30^\circ = \sqrt{3}/2$]

In Young's double slit experiment, the wavelength of light used is $\lambda$. The intensity on the screen at a point for path difference '$\lambda$' is 'X'. The intensity at the point for path difference $\left(\dfrac{\lambda}{6}\right)$ is ($\cos 180^\circ = -1$, $\cos 30^\circ = \dfrac{\sqrt{3}}{2}$)

In a single slit diffraction pattern, the distance between the plane of the slit and the screen is $1.4$ m. The width of the slit is $0.66$ mm. The second maximum is formed at the distance of $2.8$ mm from the center of the screen. The wavelength of light used is