A pinhole camera can also be used to create photographic images. If light sensitive film is left in the camera and the camera left focusing on one image then after a while a black and white image will develop itself on to the film. This is therefore a very crude way of taking a picture. It can also be used to take pictures of outer space as it picks up the light and can show the placement of stars. I myself have used this method to produce an image of a solar eclipse on to a piece of paper so I could view this image of the eclipse safely.
In the museum I also saw an exhibit called Painting with Light.
In this exhibit we had a pen which had lots of optical fibres inside, we then put this onto a screen and made shapes with it, this then made the screen in the parts exposed to the light from the fibre optics glow green. The material of the screen then captured this light and it slowly faded and disappeared. Fibre optics can be used in a number of practical applications. They are very important in telecommunications, this is because they have high carrying capabilities, low power, they can carry digital signals which is very important in the modern world, light in weight, flexible and most importantly cheap compared to the old copper wiring that was originally used. So the telecommunications companies use these lot now as the have many advantages and also save them money. They are also used to inspect dangerous places for example the police might use them to view inside a building where there is a hostage situation or a bomb. So they also help to save lives.
A fibre optic works to transmit light is basically to have a thin wire and line it with reflective cladding. Then you angle the beam of light into the tube so that the angle is just right and so the beam will bounce off all of the sides to the other end. The light in a fibre optic is constantly travelling through the core by a principle called total internal reflection (TIR). This means that the angle the light hits the walls of the optical fibre has to be more than the critical angle of the material.
CRITICAL ANGLE DIAGRAMS
This shows the light moving from more dense to a less dense medium until total internal reflection takes place. This experiment shows the light beam travelling through a glass block.
Refraction at the glass as I increases, r If I>c, all light
The glass air boundary also increases is reflected
When I=c (critical angle) internally
R=90 degrees within the glass
TIR occurs
I = angle of incidence r= angle of reflection
These diagrams show how in the optical fibres that the critical angle and the angles that the beam enters the fibre is important for it to create total internal reflection and be able to let the beam travel all the way along the optical fibre.
This diagram shows the way in which the critical angle is used within the fibre optic. The critical angle in a fibre is described as the parallel axis running down the middle of the fibre. This therefore the critical angle is 90 degrees as the diagram shows and for the fibres to work the angle needs to be bigger than 90 for total internal reflection to occur.
A fibre optic can be used as well to go around corners as seen below in this diagram. This is all done by total internal reflection.
In researching about fibre optics in the museum and from other sources including textbooks and the internet I have found out that they have many uses in industry including telecommunications, areas of work where surveillance is necessary including police work, and also in the home in leisure things like tree lights. They do all these things and have made life easier for some lines of work where in the past problems occurred. They have helped in many ways and they are basically based around and made to work using a basic physics principle.
The positives of fibre optics are clearly present and greatly outweigh the bad points. However there are some, the problems can include because you are working with such small wires they can be very fragile and one breakage in the line can ruin the whole cable if it is being layed somewhere and also to repair it is hard to find the actual point where the line is damaged.
However optical fibres are a great advance in technology and I expect that they will carry on being used for a long time yet due to its range of uses and the advantages people can get from them.
