Question

Monochromatic light of wavelength ${\lambda }_1$ travelling in a medium of refractive index ${\mu }_1$ enters a denser medium of refractive index ${\mu }_2$. The wavelength in the second medium is:

• A. ${\lambda }_1\left({\mu }_1/{\mu }_2\right)$
• B. ${\lambda }_1\left({\mu }_2/{\mu }_1\right)$
• C. ${\lambda }_1({\mu }_2-{\mu }_1)/{\mu }_2$
• D. ${\lambda }_1({\mu }_2-{\mu }_1)/{\mu }_1$

Answer 1

The correct option is A ${\lambda }_1\left({\mu }_1/{\mu }_2\right)$

${\lambda }_a=\frac{c}{v}$ or ${\lambda }_m=\frac{v}{v}=\frac{c}{{\mu }_{m}v}(\because {\mu }_m=\frac{c}{v})$
$\therefore {\lambda }_1=\frac{c}{{\mu }_{1}v}$ and ${\lambda }_2=\frac{c}{{\mu }_{2}v}$
or ${\lambda }_1{\mu }_1={\lambda }_2{\mu }_2$ or ${\lambda }_2={\lambda }_1\left({\mu }_1/{\mu }_2\right)$