Is the idea of negative absolute temperature analogous to a virtual image?

In summary, the concept of negative absolute temperature can be compared to the idea of a virtual image in geometrical optics, where the reciprocal relationship between temperature and entropy is similar to the relationship between distance and focal length in an optical system. Just as a real image becomes a virtual image at infinity, a material with negative temperature exhibits similar behavior. This comparison is supported by mathematical observations.
  • #1
swampwiz
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Is the idea of negative absolute temperature analogous to a virtual image in geometrical optics?

I was reading this article about such a negative temperature:

http://www.livescience.com/25959-atoms-colder-than-absolute-zero.html

It seems to me that since temperature is defined by its relationship to entropy, its reciprocal is the key expression. Similarly, the distance of an object, image or focal length in an optical system is related as per their reciprocals. The way it works is that as the distance of a real (i.e., positive-valued) image goes to positive infinity, it crosses over to negative infinity, at which time it changes from a real image to a virtual image. This seems to be the observed behavior, mathematically speaking, for this material having a negative temperature.
 
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  • #2
That seems to me to be an eminently reasonable comparison.
 

1. What is negative absolute temperature?

Negative absolute temperature is a concept in thermodynamics that refers to a state where the temperature of a system is below absolute zero, which is the lowest possible temperature on the Kelvin scale.

2. How is negative absolute temperature different from positive absolute temperature?

Positive absolute temperature corresponds to a state where the particles in a system have more energy as the temperature increases, while negative absolute temperature corresponds to a state where the particles have less energy as the temperature increases.

3. What is a virtual image?

A virtual image is an image that appears to be in a different location than the actual object, but is not formed by the convergence of light rays. It is created by the reflection or refraction of light, where the rays appear to originate from a point behind the mirror or lens.

4. How is the idea of negative absolute temperature similar to a virtual image?

In both cases, the concept of "negative" is used to describe a state that is opposite to the norm. Just as a virtual image is an apparent image that is opposite to the actual physical location of an object, negative absolute temperature is a state that is opposite to the typical behavior of particles at higher temperatures.

5. What are some real-life examples of negative absolute temperature?

Some examples of systems that can exhibit negative absolute temperature are certain laser-cooled atoms, spin-polarized nuclei, and ultracold Bose-Einstein condensates. These systems have been observed to have negative temperatures on the Kelvin scale, but it is important to note that this does not mean they have a temperature below absolute zero on the Celsius or Fahrenheit scales.

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