A Pigment Absorbs a Photon If the Energy of the Photon

Question

A pigment absorbs a photon if the energy of the photon is ____.  
A) exactly enough to boost an electron of the pigment to a higher energy level
B) slightly more than the energy of the electron absorbing the photon
C) significantly more than the energy of the electron absorbing the photon
D) exactly twice the energy of the electron absorbing the photon
E) significantly less than the energy of the electron absorbing the photon

Accepted Answer

A pigment molecule will absorb a photon of light only if the energy of the photon is exactly equal to the energy gap between the pigment's ground state and an excited state. This energy gap corresponds to the energy difference between the electron’s current orbital and the higher energy orbital the electron will move into upon photon absorption. If the photon has less energy than this gap, it will be unable to excite the electron, and if it has more energy, the excess energy is wasted and not utilized by the pigment.