Which statement best explains why infrared radiation is typically able to excite…
CHEMISTRY · Single correct · A Level · Chemistry · Organic analysis and spectroscopy · Organic analysis and spectroscopy
Problem
Which statement best explains why infrared radiation is typically able to excite vibrational transitions in molecules, whereas microwave radiation generally is not?
(a) The speed of infrared photons is greater than that of microwave photons, so IR photons deliver more energy to the molecule and can trigger vibrations whereas microwaves cannot.
(b) Vibrational energy‐level spacings are much larger than rotational spacings, so photons must have higher energy (shorter wavelength) than microwaves provide.
(c) Vibrational transitions actually require less energy than rotational transitions, placing them in the infrared rather than the microwave region.
(d) Only infrared photons are able to induce a changing dipole moment in a molecule, a requirement for absorption; microwave photons cannot create such dipoles.