Question

What is Fresnel biprism?

Answer 1

Young's Slits is a variation on the Fresnel Biprism experiment. Two thin prisms are joined at their bases to produce an isosceles triangle in the Fresnel biprism. A single wavefront impinges on both prisms, with the left segment refracted right and the right segment refracted left. Interference occurs in the superposition area because two virtual sources exist.

Complete answer:
The Fresnel biprism illustrates light interference. It's a twist on Young's renowned double-slit experiment. The isosceles triangle was created by joining two thin prisms at the base to create a very small refracting angle of ${0.5^o}$ . The Fresnel biprism is used to determine the thickness of a thin film, the medium's refractive index, and the wavelength of the light source, among other things.
We must assume that the slits serve as point sources in the Young's slits experiment. However, because the slits have a finite width, this is not the case.
The secondary slits' finite size creates undesirable diffraction effects, which create mistakes. By substituting prolonged secondary slits with virtual slits that are point-like, the Fresnel biprism solves the problem of prolonged secondary slits.
Biprism also known as Fresnel biprism — a triangular prism with a vertex angle of roughly $180^\circ$ used to obtain images of a single source in detecting light interference.

Note:
We were able to compute the wavelength of the sodium light which is given by
$6.1{\text{ }} \times {10^{( - 7)}} \pm 1.6{\text{ }} \times {10^{( - 7)}}$ m using the Fresnel Biprism method, which is within experimental error of the recognised estimate of $5.9 \times {10^{( - 7)}}m$ . Although this method is more accurate than Young's Slits, a better technique of determining the fringe separation might produce an even more exact answer.