Solution:
Given:
initial orbit of electron= [tex]n_{i}=5[/tex]
final orbit of electron= [tex]n_{f} =2[/tex]
to find wavelength we use Rydberg equation:
1/λ [tex]=R(1/n_{f} ^2-1/n_{i} ^2)[/tex]
where R is Rydberg constant and it's value is [tex]R= 1.0973*10^7/m[/tex]
inserting all the values in formula
1/λ[tex]=(1.0973*10^7)(1/2^2-1/5^2)[/tex]
λ[tex]=3.14*10^-^7m= 3.14*10^-^5 cm[/tex]
for it's region and color look at given attached pictures
