What Happens to Lasers Underwater? (Total internal reflection) - Smarter Every Day 219

TL;DR

This video showcases the fascinating phenomenon of Total Internal Reflection using lasers and water, demonstrating how light bounces off different surfaces underwater.

Transcript

• Hey it's me Destin. Welcome back to Smarter Every Day. If you can't tell, I am on a kayak here. And we have a lot of the kayak. I guess it was a week ago I uploaded a video to the second channel. And we were trying to fish, right Trent? - [Trent] Yeah. - Oh you're over there. - [Trent] I'm over here. - So we were fishing because we've been workin... Read More

Key Insights

• 🙂 Total Internal Reflection occurs when light passes from a dense medium to a less dense medium at an angle greater than the critical angle, causing the light to reflect instead of refract.
• 🙂 Snell's window is an area above water where a diver can see light from certain angles, while beyond that angle, the light reflects out.
• 🙂 Acrylic and fiber optics can demonstrate Total Internal Reflection when laser light is directed at certain angles inside the materials.
• 🙈 Total Internal Reflection can be seen when lasers are shined into water-filled objects, such as a Christmas ornament, resulting in various reflections and refractions.
• 💿 Understanding Total Internal Reflection can have practical applications, such as in fiber-optic communication systems.
• 😃 It is important to wear appropriate eye protection, such as laser goggles, when working with lasers to prevent eye damage.
• ❓ Exploring scientific phenomena in everyday settings, like kayaking, can make learning more engaging and enjoyable.

Questions & Answers

Q: What is Total Internal Reflection?

Total Internal Reflection is a phenomenon where light passes through a medium and hits a boundary at an angle greater than the critical angle, causing the light to reflect instead of refract.

Q: How does Snell's window work?

Snell's window refers to the region above the water surface where a scuba diver can see the sunlight from a certain angle, while beyond that angle, the light reflects out due to the difference in refractive index between water and air.

Q: How does Total Internal Reflection work with acrylic?

When the laser beam hits the inside of a square acrylic block at an acute angle, it reflects multiple times off the interior surfaces due to Total Internal Reflection, causing the entire block to light up.

Q: What did they observe when shining lasers into water-filled fiber optics?

The lasers propagate down the fiber optics due to Total Internal Reflection, effectively acting as a light pipe.

Summary & Key Takeaways

• The video begins with the host and a friend kayaking, and they decide to play around with their headlamps underwater. They discover the concept of Snell's window and how light behaves in water.

• They then proceed to experiment with lasers and different materials, such as acrylic and fiber optics, to observe Total Internal Reflection and how light bounces inside these materials.

• Lastly, they test the Total Internal Reflection in water by shining a laser into a Christmas ornament filled with murky water, showcasing the different angles of incidence and how they affect the path of the light.