Optics Question 849
Question: In Fresnel’s biprism experiment the width of 10 fringes is 2cm which are formed at a distance of 2 meter from the slit. If the wavelength of light is $ 5100\overset{o}{\mathop{A}} $ then the distance between two coherent sources will be
Options:
A) $ 5.1\times {{10}^{-4}}m $
B) $ 5.1\times 10^{4}m $
C) $ 5.1\times {{10}^{-4}}mm $
D) $ 10.1\times {{10}^{-4}}cm $
Show Answer
Answer:
Correct Answer: A
Solution:
[a] $ d=\frac{D\lambda }{\beta } $ …(i)
According to question, $ \lambda =5100\times {{10}^{-10}}m $
$ \beta =\frac{2}{10}\times {{10}^{-2}}m $ …(ii) D=2m, d=?
From eqs. (i) and (ii) $ d=\frac{2\times 51\times {{10}^{-8}}}{2\times {{10}^{-3}}}=5.1\times {{10}^{-4}}m $
