Answer:
The value of wavelength is , [tex]\lambda=399\ nm.[/tex]
Explanation:
We know ,
For Balmer series :
[tex]\dfrac{1}{\lambda}=R(\dfrac{1}{2^2}-\dfrac{1}{n^2})[/tex]
Here , R is Rydberg constant , [tex]R=1.09\times 10^7\ m^{-1}.[/tex]
Therefore , [tex]\lambda=\dfrac{1}{R\times (\dfrac{1}{2^2}-\dfrac{1}{n^2})}[/tex]
Here , [tex]\lambda[/tex] should be less than 400 nm and should be the lower limit for wavelengths in the visible spectrum.
Putting n = 7 .
We get ,
[tex]\lambda=\dfrac{1}{1.09\times 10^7\times (\dfrac{1}{2^2}-\dfrac{1}{7^2})}\\\lambda=399 \ nm.[/tex]
Hence , this is the required solution.
