Answer
656.5 nm
Work Step by Step
1
The least energetic spectral Line for Hydrogen in the VISIBLE range can be obtained when an Electron in H atom jumps from Level 2 to Level 3.
Now,
Rydberg's Equation is given as :
1/ λ = R [1/(n1)² - 1/(n2)²]
Where,
λ : Wavelength
R : Rydberg's Constant = 1.0967 x 10^7 / m
2
Solution :
Here,
n1 = 2
n2 = 3
Substituting the values in the Rydberg's formula,
1/ λ = R [1/(2)² - 1/(3)²]
1/ λ = 1.0967 x 10^7 x [1/4 - 1/9]
1/ λ = 1.0967 x 10^7 x (5/36)
1/ λ = 1.52 X 10^6 / m
λ = 6.565 x 10^-7 m
λ = 656.5 nm
