Blue Ain’t Your Color (Part 2)

It’s Rima the white antelope again, coming back for the second instalment of Blue Ain’t Your Color.

If you missed out on Part 1, check out Blue Ain’t Your Color (Part 1). (You don’t really need to read that first in order to understand this though.) If you insist on not reading Part 1, I’ll just let you know that the inspiration behind this post is a lyric from the song Blue Ain’t Your Color, covered by Home Free, originally done by Keith Urban.

How do neon lights work?

Inspired by the lyric: (Blue) looks good on that neon buzzin’ on the wall

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Blue Neon Lights. Image from: Panik Design

Atoms in neon lights – or gas discharge tubes – are responsible for the colour we see illuminating from these lights. Inert gases like neon (hence the name neon lights) are used as their atoms do not react with each other.

It’s all in the atoms

As we all know, atoms are tiny particles which make up everything. The actual model of an atom is highly complicated, but for the purpose of this concept, we can think of an atom as a solar system, with the nucleus (made up of neutrons of no charge and protons of positive charges) of the atom as the sun (the core of the system) and the electrons (negative charges) as the planets orbiting it. These electrons are arranged in shells, or energy levels. The higher the energy an electron has, the father it is from the nucleus.

Lithium_Atom

An example of a model of an atom. Image from http://www.antonine-education.co.uk/Pages/Physics_1/Particles/PP01/Particles_Page_1.htm

An example of a model of an atom. Image from http://www.antonine-education.co.uk/Pages/Physics_1/Particles/PP01/Particles_Page_1.htm

The light-making process is as such (illustrated by the figure below):

  1. When atoms are stable, electrons (blue dots) are in their ‘resting positions’, or more technically known as ground state.
  2. When they absorb energy, some of these ‘resting’ electrons get excited, moving to a higher energy level, or a farther electron shell.
  3. But they do not remain there for long as an excited atom is an unstable one and would so desperately want to go back to being stable. This means that the excited electron has to return to its ground state. So where does this extra energy go to? It is being released as a photon or a packet of light (green squiggly line).

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Light-making process of an atom. Image from http://www.explainthatstuff.com

Where did all that energy come from?

We will need to know what are the components of a neon lamp.

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Components of a neon lamp. Image from http://www.explainthatstuff.com
  1. The neon gas is encased in a glass tube.
  2. At the end of the tube, there are electrical terminals at both ends. One end is a negative terminal (-ve) and the other is a positive one (+ve).
  3. If the tube is not switched on, i.e. there is no voltage across the terminals, the neon atoms will just be neon atoms (brown dots).
  4. When the tube is switched on, i.e. a high voltage applied across the terminals, the atoms go crazy (kind of). Some atoms will lose electrons to become positively charged (green dots) and will be attracted to the negative terminal.
  5. The electrons (blue dots) that were lost will be attracted to the positive terminal.
  6. As charged atoms and electrons move to their respective terminals, they will always be colliding with one another (imagine the chaos). These collisions give rise to energy which excites the atoms, making them produce photons (red squiggly line) like what we discussed above.
  7. These surge in energy also brings about heat, which explain why you shouldn’t touch neon lamps.

Technically, blue looks good on that argon buzzin’ on the wall

Neon atoms will actually produce red light, and it is actually argon that will glow blue. This is because each noble gas – or every atom for that matter – has a characteristic colour of light.

If we refer to the model of the atom brought up earlier, the electron shells are predetermined by the atom itself. A neon atom will have set of electron shells of certain values and argon will have another set of shells. This means that electrons can only absorb and emit a certain and precise amount of energy according to these electron shells, which correspond to a certain wavelength of visible light.

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Due to the difference in the energy levels, neon and argon glow different colours. Image from http://www.explainthatstuff.com

If you fancy having neon signs in your vicinity, Signarama can get you neon signs and other kinds of signs! Or you can go for Neon Lights 2017: Two days and six stages of music, art and fun in the Lion City, happening this November. Needless to say, these are not paid endorsements, I just insist on including these in my posts.

Reference

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