The n = 2 to n = 6 transition in the bohr hydrogen atom corresponds to the of a photon with a wavelength of nm.

The energy levels of the hydrogen atom are quantized and their energy is given by the approximated formula

where n is the number of the level.

In the transition from n=2 to n=6, the variation of energy is

Since this variation is positive, it means that the system has gained energy, so it must have absorbed a photon.

The energy of photon absorbed is equal to this . Converting it into Joule,

The energy of the photon is

where h is the Planck constant while f is its frequency. Writing , we can write the frequency f of the photon:


The photon travels at the speed of light, , so its wavelength is


So, the initial sentence can be completed as:
The n = 2 to n = 6 transition in the bohr hydrogen atom corresponds to the "absorption" of a photon with a wavelength of "411" nm.