Question

Air has refractive index $1.0003$. The thickness of the air column, which will have one more wavelength of yellow light ($6000A^o$) than in the same thickness of vacuum is

• A. $2mm$
• B. $2cm$
• C. $2m$
• D. $2km$

Answer 1

Answer: (A)

$2mm$

Let $x$ be the thickness, then

$\frac{x}{{\lambda }_a}=\frac{x}{{\lambda }_v}+1$ and ${\lambda }_a=\frac{{\lambda }_v}{\mu }$

$\Rightarrow x=\frac{{\lambda }_v}{(1-\mu )}=\frac{6\times {10}^{-7}}{0.0003}=2mm$