Alternative Explanation to Light and Color

One problem in physics that has always intrigued me is color. What is color? Why is something one color, and another a different color even though the same light is hitting both objects? In grammar school and high school, I remember my teachers telling me that a leaf is green because it absorbs all other colors of light, and reflects only green light. This explanation never made sense to me and I never believed it. I have always wondered what happens to light on a microscopic level that causes only certain colors to bounce back into our eyes.
As you know, light from the sun is made up of all colors: red, orange, yellow, green, blue, indigo, and violet. Well, there are other “colors” as well, but the human eye cannot see them; these include ultraviolet, infrared, microwave, gamma rays, etc. In physics, we do not refer to these as colors but rather electromagnetic waves. The portion of the electromagnetic spectrum that humans can see is referred to as visible light, or color. Each color has a certain energy value and a certain frequency of oscillation (vibration) associated with it. The frequencies of visible light range from 7.5 x 1014 (violet) to 4.3 x 1014 (red).
When we begin to look at things microscopically, we begin to see that everything oscillates, or vibrates. Atoms, when bonded together to form a molecule, act as objects connected together by springs, free to bounce back and forth, or oscillate. What exactly are bonds between atoms?: Nothing more than electrons being shared between the atoms, in ionic cases. Each type of molecule has a unique pattern of atoms and bonds, making it oscillate in its own unique way. Furthermore, physics has discovered a property called the photoelectric effect. When light shines on an object, it excites (moves more rapidly than normal) the electrons on its surface. Why does this make sense? Well, light is made up of electricity and magnetism. Basically, throwing electrical forces at electrons makes them move. Physicists find this fascinating; I’m not surprised, are you? So we know two things: all materials vibrate microscopically and all materials are affected electrically by light. If we combine the two ideas, we can say that bonds are affected by light, and therefore light has an effect on the way molecules vibrate.
Still not seeing the big picture? Well, let’s pretend we are a ray of yellow light vibrating along through the air toward a banana (a ripe one). Fact: yellow light happens to vibrate 5.2 x 1014 times per second. The molecules in the banana are joined in a way that vibrating at 5.2 x 1014 times per second really tickles their fancy. In physics, this is called resonance. The banana molecules vibrate more easily at 5.2 x 1014 times per second than at any other frequency, so when yellow light hits them, they really start moving! This allows the yellow light to bounce off the molecules more efficiently than all the other colors of light. This is much like double-jumping someone on a trampoline; when you jump at the same time, you end up bouncing higher! So now, let’s imagine that we are yellow light vibrating along towards an orange (or tangerine, or cutie). Since the orange molecules don’t like to shake it like we like to shake it, our frequencies clash and the light just doesn’t bounce the same. This is much like dancing with someone who is off beat.
Here is the coolest part. Since color depends directly on chemical bonds and atomic structure, it can really tell us a lot about the molecular makeup of just about anything! You may have heard about this in your chemistry class. In chemistry (and physics), we use spectrometers to capture light that is bouncing off a substance to generate spectral lines. Each element in the periodic table has a unique set of spectral lines. These lines are nothing more than an indication of which colors resonate with a certain substance. In other words, the lines indicate which vibration frequency tickles the atoms or molecules fancy. To further investigate color, we can think about materials that are clear or translucent: like a diamond. Diamonds have a very rigid structure, making it difficult for the molecules to vibrate. If the molecules don’t vibrate, then we do not see any color. All objects resonate at more than one frequency, including frequencies that are not part of the visible spectrum. However, by using infrared or thermal imaging cameras, we can “see” those vibrations and translate them into a temperature reading.
How many other properties can be determined by color? To my knowledge, we have measured chemical makeup of stars, the speed of galaxies in the universe, temperature, electrical properties of materials, photosynthesis, and I am sure many more. Knowing the relationship between light and physical objects opens up many possibilities in science. Understanding it is the first step.