Sodium light $\left(\lambda=6 \times 10^{-7} \mathrm{~m}\right)$ is used to produce interference pattern. The observed fringe width is 0.12 mm . The angle between the two wave trains is

A plate of refractive index 1.6 is introduced in the path of light from one of the slits in Young's double slit experiment then

In Young's double slit experiment, the intensity of light at a point on the screen where the path difference is $\lambda$ is x units, $\lambda$ being the wavelength of light used. The intensity at a point where the path difference is $\frac{\lambda}{4}$ will be $\left(\cos 2 \pi=1, \cos \frac{\pi}{2}=0\right)$

In double slit experiment, instead of taking slits of equal widths, one slit is made twice as wide as the other. Then in interference pattern