The of the
When dropping from the second vibrational level to the first, energy will be released, since the second vibrational level is higher in energy than the first.
The difference in energy between the two vibrational levels will be equal to the energy of the emitted photon. So,
By definition, a photon's energy is proportional to its frequency according to the equation
So, plug your values into the equation and solve for
If you want, you can express the frequency in Hz, which means that you'll have