How does visible light interact with different materials?
Light can interact with matter in three ways: absorption, transmission, and reflection. 1. ABSORPTION – When a light wave with a identical frequency to an electron’s natural frequency “impinges” upon an atom, the electrons will begin to vibrate as a result (almost like they are “set in motion”). The electrons will absorb the light wave (because it has the same vibrational frequency) and turn it into a vibrational motion (sort like it “matches” with the vibrational waves). The electrons, in turn, bump up against neighboring atoms, which changes the vibrations intothermal energy (think of when one cheering section at a baseball game starts doing the “wave”, which prompts all the other section to join in the fun). This thermal energy is not turned back into light energy, thus that particular light wave never leaves the object again. This is ABSORPTION.
2. REFLECTION – This occurs when the frequency of the incoming light wave does not match that of the electrons’ natural frequency. If the object is opaque (not see-through/solid color), the electron vibrations are not “passed down” like during absorption. Rather, the surface-level electrons vibrate briefly before emitting that wave back out (as light). This is REFLECTION.
3. TRANSMISSION – Transmission works along the same lines as reflection, except it involves transparent or semi-transparent objects. The atoms take in the wave, vibrate briefly (but at a small amplitude – not like during absorption, when they vibrate with large amplitudes), transfer the vibrations throughout the body of the material, and then re-emit the wave as light out the other end. This is TRANSMISSION.
