Refraction in water | Geometric optics | Physics | Khan Academy

TL;DR

Refraction of light when it passes from one medium to another is the reason why the straw appears bent in the picture.

Transcript

Before doing more examples with Snell's Law, which essentially amount to some math problems, what I want to do is get an intuitive understanding for why this straw looks bent in this picture right over here. To do that, let me just draw a simplified version of that picture. So let's draw, this is the cup right over here. We'll do a side profile of ... Read More

Key Insights

• 🙂 Refraction occurs when light passes through different mediums and causes changes in its direction.
• ✈️ Light moves slower in water and faster in air.
• 🙂 The optical illusion of a bent straw in a glass is due to the way our brain perceives the refracted light rays.

Questions & Answers

Q: Why does the straw in the picture appear bent?

The straw appears bent due to the refraction of light as it passes from air to water, causing the light rays to change direction and create an optical illusion.

Q: Why does light bend when it passes from one medium to another?

Light bends because the speed of light changes when it moves from a slower medium (like water) to a faster medium (like air), causing a change in its direction.

Q: How does our brain perceive the location of the bent straw?

Our brain assumes that light travels in a straight line, so when it traces the refracted rays back to their apparent origin, it perceives the straw to be bent.

Q: Can the same refraction principle explain other optical illusions?

Yes, similar principles of refraction can explain various optical illusions, such as the appearance of objects being closer or farther away in water than they actually are.

Summary & Key Takeaways

• The video explains the optical illusion of a bent straw in a glass due to the refraction of light.

• Light moves slower in water than in air, causing the light rays from the straw to change direction when they pass through the water.

• When our eyes trace back the refracted rays, it appears as though the straw is bent, even though it isn't.