Question

In a Fresnel biprism experiment, the two positions of lens give separation between the slits as $16$cm and$9$cm, respectively. What is the actual distance of separation?

• A. $12.5cm$
• B. $12cm$
• C. $13cm$
• D. $14cm$

Answer 1

Answer: (B)

$12cm$

A Fresnel Biprism is the variation on the Young's Slits experiment. The Fresnel biprism has two thin prisms which are joint at their bases to form an isosceles triangle. A single wavefront impinges on both prisms.

Separations between the slits,

$d_1=16cm$

and $d_2=9cm.$

Actual distance of separation (d) can be computed with the formula as given:

$d=\sqrt{d_1\times d_2}$

$d=\sqrt{16\times 9}$

$d=\sqrt{144}$

$d=12cm$

Thus actual distance will be $12cm$.

Option B is correct.