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Choosing a light source

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Choosing a light source

Task 1:


  • Filament light


  1. Coiled tungsten filaments are the metal wires that glow brightly when electricity flows through them.
  2. Connecting wires are the wires that carry electricity from the bulb's electrical contact to the filament.
  3. Electrical contacts - the metallic base of the bulb, which connects to the electrical contacts of the lamp when the bulb is in the lamp.
  4. Glass envelope - the thin layer of glass that surrounds the light bulb mechanism and the inert gases.
  5. Glass fuse enclosure - glass that insulates the bulb's fuses - located in the stem of the bulb.
  6. Mixture of inert gases at low pressures - the bulb is filled with inert (non-reactive) gases.
  7. Screw cap - the threaded base of the bulb that secures it to a lamp.
  8. Support wires - wires that physically hold up the filament.

Incandescent lamps or bulbs are the most commonly used type of lighting. When electric charge passes through any component with electrical resistance, electrical energy is transformed into heat energy. The Filament gets so hot (white hot) that it gives off light.

Almost all of the electrical energy is converted into heat rather than light. Standard incandescent bulbs only last about a thousand hours and must be regularly replaced. Incandescent lamps are most suitable for areas where lighting is used infrequently and for short periods, such as laundries and toilets.image14.png


They are inexpensive to buy and are available in a wide

range of shapes and sizes.


But their running costs are high and also they intend to burn out

If drop on the floor or been switch on without care.


  • Halogen lights

Halogen lights are also similar to incandescent lamps. The halogens in the bulbs prevent evaporated tungsten from depositing on the glass bulb.

...read more.



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(2)   image20.pngnm  

The kinds of values we can expect to obtain are small/ big.

Task 4:Plan


Aim:   I will be investigating 5 coloured light bulbs with each different power (watts)

Planning for the experiment

My Predication:

I predicted that, the higher the power the greater intensity, and the less intensity the lower the brightness. Also the further distance the light source an object the less brightness observed.

For period: 1, 2 and 3

I will be carrying out my investigation using the same method. I will also be investigating two different light sources in period 1 & 2. But in period 3 I will be doing the experiment for one light bulb pulse its graph; if I don’t finish in time during this lesson (the graph), then I will have to continuo with it in period 4.

These are the light bulbs am hoping to use for my investigation:

  1. Red  (has 3.5v)                      4) White (has 6.5v)
  2. Royal blue (has 2.5v)             5) Green (has 12v)
  3. Orange (has 6v)

My method of carrying out the experiment/s:

I will be collecting all the apparatus that I will be needing e.g. they are


  1. 2x clamp stands with two clamps
  2. 1 meter ruler (wooden)
  3. 5 different light bulbs with different voltages (they are ready bering labelled with different colours)
  4. A light meter
  5. A power pack and some leads
  6. Small table lamp
  7. A black tube with two wires coming out of it (at the back)
  8. A lamp holder with connected from both ends  

Then I will set-up my apparatus as shown below:

After setting up my apparatus I will then choose to use either the light meter or the LDR (light dependent resistance) to start the experiment with. But

...read more.



Streetlights are bright at night.  Most of the streetlights are yellow coloured (sodium) and some are purple coloured (mercury). They last for the whole night, it run from about 250 volts.  They came in all different sizes and shapes.


It lets you see certain objects in yellow at night; the same principle applies to the mercury one.

Neon lights

Neon lights are small tubes with a power supply that runs from 12 volts.Electricity passing through the gas knocks electrons from their orbits. When the electron flies back into the orbit of its atom, energy in the form of a bright red light is released. This light energy is the source of the tube's glow. At both ends of the neon tubes there are metal electrodes and when you let a high amount of voltage to the electrodes, the neon gas ionises, and electrons flow through the gas. These electrons excite the neon atoms and cause them to emit light that we can see. Neon emits red light when energized in this way. Other gases emit other colours.  Neon lights reduce light pollutions by been designed small and run from small amount of volts.


Neon lights are small tubes with a power supply that runs from 12 volts. They are designed for places that are dark and also for cars too.


Neon lights only give out certain amount of light in different ranges of colours of the spectrum; therefore it’s not enough for us to see the colours of the objects very clearly.

Energy efficient lights

Energy efficient lights are smaller version of fluorescent lights. They are also designed for places where fluorescents tubes lights can’t fit.

The Advantages and Disadvantages for these types of light are the same to fluorescent tube lights (see above)

...read more.

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