Choosing a light source

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Task 1

As a part of this tasks, I will conduct a survey to show the way in which light is produced in the following types of lights;-

  • Domestic
  • Industrial/commercial
  • Outdoor


For the domestic lights, I have used house hold light bulbs which are made from a tungsten wire. the tungsten wire is placed inside a glass so that when it is heated, it does not react with oxygen to produce a oxide. The diagram below shows a tungsten light bulb.    

the voltage that is passed though the power supply goes to the tungsten wire and interferes with the atomic structure of the electrons on the atom of the tungsten. this is because the voltage is energy, and this energy moves the electrons for the orbital of the nucleus of the atom. If one of the electrons in the shells of the atom move out of place, then this must be replaced by another one straight away to keep the orbital of the electrons around the nucleus right. So to do this, one of the electrons from the outer shell of the atom jumps in to the place of the atom that was knocked out by the voltage. In doing so, a photon of energy is passed out. This photon is the light we see when we turn on a bulb.  

The tungsten metal is a good metal to be used for this kind of job. This is because tungsten has a high atomic number. This means that there are more shells of electrons. More electrons would mean that more photons can be produced from this metal which make it idle and give it a high melting point.

The tungsten has to be placed in a glass container. This is to stop oxygen coming in to the bulb and reacting with the tungsten. the glass is filled with a noble gas like argon. This is because argon does not react.        

The process by which the tungsten bulb produces light is called incandescence.

Advantages and disadvantages of using a tungsten light bulb


The halogen light bulb is used in industries to light up the areas of work. The reason for using halogen light in the place of work is because they have a longer life. This is important because in industries, lights are always on.

Below, I have drawn a diagram of a halogen lamp.


With normal tungsten lights, they are filled with noble gases. This is so that the tungsten does not react with the gas that in the glass container. With normal light, when the tungsten wire gets hot, some of its particles of the evaporate from the wire and stick to the side of the glass that holds the wire. This makes the glass cloudier and allows less light to get though. This means that with time, the amount of light transmitted by the light bulb is reduced. This is called lumen maintenance.

With halogen light bulbs, the gas that is in the bulb is different from the normal light bulbs. Mostly halogen light bulbs contain iodine of bromine. When the tungsten evaporates from the surface at high temperatures, it combines with the halogen gases. For the tungsten to stay combined with the halogen gases, the temperature of the surrounding must be 200OC. this stops the tungsten partials from condensing on the glass in with the tungsten is contained, which stops it from the glass getting cloudier. This means that the light intensity always stays the same in a halogen light unlike a normal light bulb.

With normal light bulbs, the particles of tungsten evaporate from the surface of the wire and stick to the glass side. This means that the overall amount of particles on the wire reduces. This reduces the lifetime of normal light bulbs as it comes to a point where there is too less particle of tungsten left on the wire for it to produce light.

With a halogen light, this does not happen. This is because when the temperature of the surrounding of the bulb of a halogen light drops below 200OC, all the tungsten and halogen compounds are come unstable. So when this happens, the particles of tungsten separate from the halogen gas and go and stick back to the tungsten wire. This means that less tungsten particles are lost to the surrounding which gives it a longer lifetime.  

The shape of the container that the bulb is in is different. This is more like a tube. This is so that the halogen gases are always near the tungsten wire. This allows all the particles to react with the halogens faster and to be disposed back on to the wire faster.  

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To stop the surrounding of the light bulb to rise in temperature, the halogen light bulb is contained in a stronger glass like quartz. This is because it is harder to heat up stronger glass and also it doesn’t brake easily.


Advantages and disadvantages of using a tungsten light bulb


Solar yard light are used in the outdoors. This is because the energy is made and stored from then sun and then it is used when it is dark.

Below is a diagram of a solar yard light.


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