Let There Be Light! from Mariah Tabor on Vimeo.

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Mariah Mermade Tabor, Xinyu He

Let There Be Light

The Fluorescence


Chemistry Background Information
In our common life, the electric bulbs is a common thing, while the electric bulb getting contact with electricity, a huge amount high temperature heat will be created, which is approximately 200 Celsius. Because this kind light is caused by heat, we call it "a physic light". So, if there's physical light, there absolutely a "cool light" or chemical light, and our experiment is based on "cold light".
Firefly is a kind of bug that we can see in our life, it's interesting that this bug carry a light with it all the time, if catch one of the firefly, touch the light, it doesn't feel hot at all, in fact, that bring a wired question. Like how in the world that a bug can create light, and the light is not hot at all? The answer will be Fluorescence.

An Interesting fact:
The light of a firefly is called bioluminescence. The light is referred to as a cool light because the light produces an insignificant amount of heat. The reaction taking place for fireflies light involves oxygen, which they breathe in, luciferin, containing the enzyme luciferase, and ATP (adenosine triphosphate). The catalyst is the oxygen which stimulates the luciferin and activates the luciferase. The reaction takes place in a special cell called podocytes. Fireflies are unique because the luminescence is not restricted to solely the adult species, but the larvae emit light as well. Fireflies are impressive because their method for producing light is extremely efficient. Incandescent light has about a 10% efficiency while the cool light produced has about a 96% efficiency rating.

Light, energy released by an atom, is made of small packets that act as particlas that have momentum but have no mass. These are called light photons. When an atom gets excited, it releases light photons as it come down from an excited energy level. The level of energy is dependent on several things like speed and distance from the nucleus. More often then not, electrons that are in orbitals farther away from the nucleus have a greater energy. (see picture)
A photon is whole bunch of electromagnetic energy(light) combine together. Photons are always moving in a vacuum place, because of that it has a constant speed of light to all observers, at the vacuum situation, the speed of light (more commonly just called the speed of light) of c = 2.998 x 108 m/s.
The Light is simply a name for a range of electromagnetic radiation that can be detected by the human eye. So what is electromagnetic radiation, then?
By using the simple words, electromagnetic radiation is basically a description of light movement. Since all the electromagnetic works as waves, people using it in the common life, for instances, the properties shown below.
  • Radio Waves
  • TV waves
  • Radar waves
  • Heat (infrared radiation)
  • Light
  • Ultraviolet Light (This is what causes Sunburns)
  • X-rays (Just like the kind you get at the doctor's office)
  • Short waves
  • Microwaves, like in a microwave oven
  • Gamma Rays
    All those waves shown above are using commonly in our life, and somehow, we can't live without it.
  • While defining what is light, it's interesting to mention our chemical substances. The major substances which is also the one causing light is Luminol, luminol is a versatile chemical that exhibits chemiluminescence, with a striking blue glow, when mixed with an appropriate oxidizing agent.(shown as the picture)
  • 180px-Luminol2006.jpghttp://science.howstuffworks.com/luminol2.htm
  • While the light comes out, that means a chemical energy appear, here's a diagram to explain how the energy works.
  • .gifhttp://www.chem.msu.su/eng/teaching/Kinetics-online/chapter6e_ad.html
  • Molecule is energetically advantageous formation (otherwise no molecules would exist). It means, that chemical substances on the energy diagram occupy positions in "wells". If we wish to carry out a reaction, i.e. to transform these substances into others, we should give sufficient energy to the reagents to surpass the "barrier" (energy of activation). And for our specific experiment we determined that the wavelength was approximately 135 nm. Using the equation
Speed of light= (wavelength) x (frequency), we determined the frequency to be about 2.2 x 10^6. From this we took the equation
Energy= (6.626x10^-27) x (frequency) and determined the overall energy for our experiment to be about 1.4 x 10^-20 Joules.

  • In our case, chemical energy is converted into a cool light. The energy that is release is absorbed by an electron which causes the electron to jump into an excited state. On the electrons way back down, the electron releases a visible photon of light. The luminol is reacting the hydrogendioxide which is acting as a buffer to form 3-aminophthalate and light. The K3Fe(CN)6 acts as the catalyst needed for the reaction. The catalyst allows for the 3-APA to be left in an energized state that quickly falls in energy level making the light visible in a dark room.
  • luminol + H2O2 → 3-APA + light
  • Chemical kinetics involves the rates at which chemical reactions occur and helps explain many natural and mechanical phenomena. For instance, kinetics explains how pharmaceuticals function in a biological system and how pollutants produced by combustion engines are converted for release into the atmosphere.

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