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There is no doubt that lasers fascinate us all. Not only are they extremely versatile, they also have the ability to travel great distances. It turns out that laser beams can be trapped within water bodies. Before you ask, it is safe to try the following experiment at home
All that is needed for this to be accomplished is a plastic bottle full of water, a laser pointer and a pin. Simply poke a hole in the bottle in order to let a water stream to shoot out without a hitch. Once this is done, aim the laser pointer through the bottle. You will notice the laser getting trapped in the waterfall before it curves downwards which is against the usually straight trajectory it takes.
University of Utah’s Department of Physics and Astronomy explained this further:
Placing one’s hand into the stream should reveal the laser light shining on your skin, and mixing in a little scattering agent (such as Pine-Sol or milk) can make the beam more visible.
This begs the question as to what exactly is going on here. It turns out that this is the phenomenon known as total internal reflection. Total internal reflection takes place as a light beam comes into contact with a medium boundary at a certain angle. It immediately bounces back instead of passes through. This continues to go on which explains why the laser remains trapped in the water. As far as physics is concerned, this concept requires a couple of things. Firstly, light should be within a denser medium. Secondly, the light should hit the medium boundary at the critical angle. This changes based on the type of medium.
So, each time you watch your favorite TV show, be thankful that the laser got trapped within the cable for this to be made possible.