01Light matches transitions
Different energies of light cause different changes: microwaves → rotation, infrared → bond vibration, UV/visible → electron transitions.
Energy and wavelength are inversely related: shorter wavelength = higher energy.
02Notebook box
c = λν, E = hν. h = 6.626 × 10^−34 J·s, c = 3.00 × 108 m/s.
Worked example: Which causes electron transitions, IR or UV? UV — higher energy.