Question

the wave length coming from sodium dource is 589 nm. what will be its wavelength in water?

Answer 1

The wavelength of light $\lambda$ in water is mathematically expressed as,
$\lambda =\frac{{\lambda }_0}{n}$
where, ${\lambda }_0$ is the wavelength of light in vacuum and $n$ is the refractive index of the water which is equal to 1.33.
On substituting the values in the above equation we get,
$$\begin{gathered} \lambda =\frac{589nm}{1.33} \\ \lambda =442.9nm \end{gathered}$$