Question

Fringes are obtained with the help of a bi-prism in the focal plane of an eyepiece distant $1$ meter from the slit. A convex lens produces image of the slit in two positions between bi-prism and eyepiece. The distances between two images of the slit in two positions are $4.05\times {10}^{-3}m$ and $2.90\times {10}^{-3}m$ respectively. The distance between the slits will be

• A. $3.43\times {10}^{-3}m$
• B. $0.343m$
• C. $0.0343m$
• D. $34.3m$

Answer 1

Answer: (A)

$3.43\times {10}^{-3}m$

As shown in the figure, $\frac{d_1}{d}=\frac{v}{u}$

Also, $\frac{d_2}{d}=\frac{u}{v}$

Hence, $d=\sqrt{d_1{d}_2}$ = $3.43\times {10}^{-3}m$