Measurement of the wavelength of monochromatic source of light with the help of Fresnel’s Bi prism

1. The wavelength of the light used in the Fresnel’s bi prism experiment is:
2. On increasing the wavelength of the light source fringe width:
3. In Fresnel’s bi Prism experiment the distance d1 is between:
4. In Fresnel’s bi Prism experiment the distance d2 is between: