BENDING THE LIGHT USING WATER-- COOL SCIENCE EXPERIMENT WITH LASER
All our school life, we've been taught that light travels in straight lines. Here's a cool experiment that'll prove that light can also bend. Or so you can make people think ;)
For this experiment, you'll need:
• Empty bottle
• A screw driver or any pointed thing
• A laser
• A bowl
• Take an empty bottle and punch a hole on the surface of the bottle.
• Make sure that the hole is made in or around the midway of the bottle.
• Put the bottle into the bowl and fill the bottle with water.
• The water starts flowing out of the bottle through the hole.
• Using the laser project the beam horizontal to the hole from the other side of the bottle.
• Notice that the laser beam follows the laminar flow of water stream.
• And the beam crashes down along with water into the bowl.
First things first, in this experiment, technically, the light does not bend. Observe the laminar flow water stream coming out of the bottle. When the water is in laminar flow the water stream acts just like fiber optic and carries the light. When the light beam hits the water stream, the laser light gets reflected inside the stream. Remember the surface of water is reflective both on its surface and below the surface. This underside reflection of water is usually seen in darkly lit environments like a fish tank).
When light leaves a denser material, in this case water, due to the change in speed it will change directions. However, when a certain angle, called critical angle, is reached, it reflects back.
Critical angle is the smallest angle of incidence for which light is totally reflected.
Total internal reflection is a phenomenon that happens when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface.
Critical angle of water is 48.8 degrees. When the angle of the beam crosses the critical angle the light does not go out of the stream and total internal reflection takes place. At the end of the stream, there is a lot of turbulence, so the continuous reflection chain breaks or scatters down and the laser light gets scattered.
Because of this phenomenon called total internal reflection, the light appears to be traveling along with the water stream.