This Weird Straw Effect | EVERYDAY MYSTERIES | Summary and Q&A

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July 4, 2019
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This Weird Straw Effect | EVERYDAY MYSTERIES

TL;DR

Looking through a straw at an object beneath water creates a lens effect, magnifying or shrinking the image depending on the direction of the straw, due to the cohesive properties of water and surface tension.

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Key Insights

  • πŸ’¦ Moving a straw up and down when looking through it at an object beneath water creates a magnification and shrinking effect, respectively.
  • πŸ’¦ This effect is caused by water sticking to the inside walls of the straw, creating a bulge or dip in the water surface that acts like a lens.
  • πŸ‘» Water's cohesive properties and surface tension allow it to form these curved shapes on its surface, resulting in temporary lenses.
  • πŸ’¦ Alcohol, having less surface tension and adhesion, does not produce the same lens effects as water.
  • πŸ’¦ The effect works better with a straw than with a larger tube due to the smaller scale and more pronounced bulge in the water surface.
  • πŸ˜ƒ Water lenses are not new and can be found in nature, such as in the human eye, or created artificially, as shown by Don Pettit in the space station.

Transcript

  • [Dianna] Thanks to Curiosity Stream for supporting PBS. So look through the straw at the coin and then move the straw up and down. - [William] Oh, wait, what? What? This is weird. Wait a second. What the heck is going on? - Hey, I'm Dianna, and you're watching "Physics Girl." I found out recently that straws are, like, really entertaining. You ca... Read More

Questions & Answers

Q: Why does looking through a straw at an object beneath water create a magnification effect?

When the straw is moved downwards, water sticks to the inside walls of the straw, creating a bulge in the water surface that acts like a convex lens, magnifying the image.

Q: Why does moving the straw upwards make the image appear smaller?

Moving the straw upwards drags the water up on the sides, creating a dip in the water surface. This results in the image appearing smaller, as if viewed through a "saggy lens."

Q: Why does this effect only work with water and not other fluids like alcohol?

Water's cohesive properties, due to strong hydrogen bonds between water molecules, allow it to form bulging shapes and surface tension. Alcohol has less surface tension and adhesion, leading to less pronounced lens effects.

Q: Why does the effect work better with a straw than with a giant tube or pipe?

The effect works best at small scales, and the straw's narrower diameter allows for a more pronounced bulge in the water surface. A larger tube or pipe would not create a strong enough lens effect.

Summary & Key Takeaways

  • When you look through a straw at an object beneath water, moving the straw downwards magnifies the image, while moving it upwards shrinks the image.

  • This effect is due to water sticking to the inside walls of the straw, creating a bulge in the middle of the water surface that acts like a convex lens.

  • Water's cohesive properties and surface tension allow it to form these curved shapes on its surface, resulting in a temporary lens effect.

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