Physics Students See The Light

"The Light Express Road" show is run by staff and postgraduate students from the University of Southampton's School of Physics and Astronomy. They visit schools and colleges, giving talks and providing information about studying physics at degree level.

On 14th of October, all grade 9, 10, IB1 and IB2 Physics students attended a physics light show. Before we entered the auditorium, we were given a glow stick and a piece of plastic. After warnings about flashing lights and strobe lasers they started a short laser show, which showed up in the mist in front of the scene and on the ceiling above us. The lecturer from the University of Southampton explained the properties of light, and how it is made up of all colours, while lasers only have one colour. The piece of plastic that we got in the beginning was, a diffraction grating, and when held up against the light, all the colours of the spectrum were revealed.

We were told that lasers have many applications today; they probably cut most of the clothes we wear, read and burn CD/DVDs, are used in welding and in barcode scanning.

Lasers are also used in optical fibres to transfer information such as phone calls and Internet. One optical fibre can transfer more than 50 terabits per second, but if the wrong combination of laser and fibre is used the laser light will escape, which they showed us with a green laser. Inside the fibres Total Internal Reflection is used to transport the light. TIR, as it is also known, was shown using a water basin, where the laser light couldn't escape because of TIR. With the right combination of laser and optical fibre, it could transfer more than 60 million TV channels at once or more simultaneous phone conversations than there are people on earth.

One of the most impressive tricks they showed us was transforming sound into light. They took a normal iPod and transformed the sound waves into a rapidly flashing laser, which was flashing faster than the human eye could see.  The laser was aimed at a receiver about 5 metres away, which made the flashing laser into sound waves, and the song was easily recognisable. The show ended off with another small laser show. After question time, we could go up to the stage and ask have a look at the laser system they used.

Sebastian Stripp
Physics Student, Year 10