Photons

[dydx]

So, i currently understand that it is best described as waves traveling through space. What i can't visualize mentally yet is how these waves travel from one atom to the next. What are the physics involved in these interactions?

 

The other day i was observing light source from my flash light, an 90 lumines one. I stuck it to my belly and several body parts and noticed how a small portion of the skin was lit with a reddish color. I figured it came from the numerous blood cells in it. But the light could only interact with a limited amount of skin, so i concluded it has to have some sort of "friction" reducing the travel distance until it was zero.

 

Any help?

[Cap'n Refsmmat]

The waves can be absorbed by atoms or reflected off of them. Light waves with the right amount of energy can be absorbed entirely by an atom, their energy used to bump an electron up to the next energy level. Light waves with the wrong amount of energy can bounce off.

 

The "friction," then, is the fact that the light is being absorbed by atoms in its way. This is the same mechanism that makes light warm things up -- it is absorbed, transferring its energy, which is felt as heat.

[dydx]

So that means when I aim it at the atmosphere it's being reflected? And does it also mean it travels faster in a vacuum?

[Cap'n Refsmmat]

Yes and yes.

 

The sky is blue because the gases that make up the atmosphere tend to reflect blue wavelengths more strongly than others; when you look up at the sky, you're seeing this diffuse reflected blue light. At sunset, when the light has to pass through the atmosphere horizontally (and hence travels through a larger distance of air), everything is lit in orange and reds -- because the blue light has been scattered out.

 

When light travels through a gas or transparent solid, it's often absorbed and re-emitted by individual atoms, and the properties of the electric field change with the property of the medium, altering the speed of the light. The speed is never greater than the speed of light in a vacuum.

[dydx]

Thank you very much! That answers my question and more. I was also theorizing about the different colors in the morning and sunset. It's more fun than just looking for the answer straight out. But I thought it was the variation of the angular interaction with the ozone layer more than the atmosphere itself. But I guess you're right, there is a significant bigger amount of volume in the atmosphere interacting with sun light than the ozone. But in the end I think you'll have to consider both for mathematical purposes.

[Cap'n Refsmmat]

Yeah, ozone behaves differently in light absorption and scattering -- hence its UV-blocking powers. There are charts you can find that give the absorption coefficients of a gas over a wide range of wavelengths.