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  • Srimoyee Mukherjee

Water- Laser Beam

Total internal reflection. No, this is not a yoga or mindfulness class. This is yet another addition to the great ingenuities of science: laser beams passing through and then getting trapped in water.

Many of us have played 'laser tag', the game where we wear unique jackets and have (laser) guns in a dark room lit with various neon lights. The jacket buzzes on contact with the laser beam. A laser beam (or laser) is a stream of focused, coherent light of a single wavelength. Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. They travel long distances and are secret superweapons of science.

Total internal reflection occurs when a laser beam is pointed at a jet of flowing water. When the laser beam travels through water, it is slowed by the heavier particles in it, effectively 'trapping' the laser beam in the water. To prove this, a simple experiment can be done at home. All you need is a plastic bottle filled with water, a pin and a laser pointer (ensure that it doesn’t reach anyone’s eyes). Just make a hole in the side of your bottle. A stream of water will smoothly flow, and then aim your laser through the bottle, and you'll see it get caught up in the waterfall and curve downwards with it, interrupting its usually straight path. The light essentially reflects rather than passing straight through.

Should laser beams be used in warfare in the future, just putting a simple glass of water (glass, plastic or any other transparent material) will efficiently trap the beam, thereby not causing any harm. Well, we can still use this trick while playing laser tag!


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