Method to find separation of slits using fresnel biprism?

To determine the actual separation of the slits (or more accurately, the separation between the two virtual sources) in a Fresnel biprism experiment, you can follow these steps:

Identify the Given Values

In the Fresnel biprism experiment, the separation between the virtual slits is not directly measurable because the slits are virtual. Instead, you measure the separation between the images formed by a convex lens placed between the biprism and the screen at two different positions.

• Let (d_1) be the separation between the two images formed by the convex lens in the first position.
• Let (d_2) be the separation between the two images formed by the convex lens in the second position.

Use the Formula for Actual Distance of Separation

The actual distance of separation (d) between the virtual slits can be calculated using the formula:

[ d = \sqrt{d_1 \times d_2} ]

Steps to Calculate

1. Measure (d_1) and (d_2): Place a convex lens between the biprism and the screen and adjust it to form real images of the virtual slits on the screen. Measure the separation between these images at two different positions of the lens.
2. Calculate the Product: Multiply (d_1) and (d_2).
3. Take the Square Root: Calculate the square root of the product to find (d).

For example, if (d_1 = 16) cm and (d_2 = 9) cm, then:

[ d = \sqrt{16 \times 9} = \sqrt{144} = 12 \text{ cm} ]145