Question

In a michelson interferometer, scale readings for a pair of maximum brightness are around 0.8434 mm and 0.9618mm. If the mean wavelength of the two lines is 6480 $\dot{A}$. The difference between the wavelength $({\lambda }_1-{\lambda }_2)$ is__________$\dot{A}$.

• A. 11.2
• B. 17.73
• C. 12
• D. 19

Answer 1

The correct option is B 17.73

${\lambda }_1{\lambda }_2=\frac{{\lambda }_1{\lambda }_2}{2x}=\frac{({\lambda }_{av}{)}^2}{2x}$

$=\frac{(6480\times {10}^{-10}{)}^2}{2(0.9618-0.8434)\times {10}^{-3}}$

$=\frac{(6480\times {10}^{-10}{)}^2}{2\times 0.1184\times {10}^{-3}}$

$=\frac{4.19\times {10}^{-13}}{2\times 0.1184\times {10}^{-3}}=17.73\times {10}^{-10}$

$=17.73\dot{A}$