Is the sun always red when it sets (excluding when there are clouds etc)?

Question

I say yes due to the light going through the atmosphere (prisms) but my other family say that it is not always red but cannot give me a reason why.

Answer 1

Sun is generally red/orange when it sets or rises, but the exact hue depends on several factors, such as the amount of dust in the atmosphere. Usually, there's more dust in the air in the evening, so sunsets usually look much more vivid than sunrises. When the air is clear, sunsets look golden-orange.

Very rarely, when the conditions are right, the last bit of the sun over the horizon will be green! It's a very rare phenomenon, though.

One correction, though: the red colour of sunsets is not due to the prism effect, it's due to the scattering of light by air and dust particles.

Answer 2

I've "heard" similar to your own thinking.  Same as why the moon when it rises and sets its orange as well....when they are lower in the horizon you are looking through more of the earths atmosphere and because color is just light that is reflected back to you at that wavelength, the more atmosphere it travels through all the other colors are filtered out except for the orange/red that you see.  

Same as the solid, dense Ice patches on glaciers. You see through it and the only color that isn't absorbed reflects back as a rich blue, the ice if thawed isn't actually blue.

Answer 3

I don't know if its the same concept as a prism, in fact prisms deal with light refraction but red sunsets deal with scattering short wavelengths of light.  I'm no expert but I think you are right that it realistically always occurs.

The reason the sun turns red is because the light travels through more of the atmosphere.  Keep in mind the atmosphere is not just some barrier a couple of miles above us, its all the air and everything contained in it between Earth's surface and space.  Also the atmosphere is most dense nearest the surface.  When the sun is near the horizon then, light must travel the through the most dense part of the atmosphere for the longest time causing a change in the Sun's color.

The Sun turns red because the blue wavelengths of light are scattered by dust and air molecules.  Bluer wavelenths have higher frequencies and shorter wavelengths and therefore are more easily scattered than red wavelengths.  Thats also why the sky is blue because blue light is scattered.  I think the high frequency of the wave is the most important factor in scattering light.

At 0 degrees the sun actually turns green for a second.  I would invite you to read more about the "green flash" phenomenon and "mirages" on wikipedia.

I'm no expert please find flaws in this explanation if there are any.  

Edit - (I lied about amplitude)