Answer: 656.6 nm.
Step-by-step explanation:
Using Rydberg's Equation for hydrogen atom:
Where,
= Wavelength of radiation
= Rydberg's Constant
= Higher energy level = 3 (least energetic for visible series)
= Lower energy level = 2
We have:
(
)
The wavelength of the photon emitted when the hydrogen atom undergoes a transition from n = 2 to n = 3 is 656.6 nm.