yego.me
💡 Stop wasting time. Read Youtube instead of watch. Download Chrome Extension

Refraction in a glass of water | Waves | Middle school physics | Khan Academy


2m read
·Nov 10, 2024

So, something very interesting is clearly going on when we look at this pencil dipped in this cup of water. We would expect if maybe there was no water in this glass that we would just see the pencil continue straight down in a line that looks something like that. But that's clearly not what we are seeing. It looks like once we fill it with water, at least to our eye, it looks like the pencil gets bent or broken or bent in some way.

This notion you might have heard people call it refraction, but it's interesting to think about exactly why this is happening. And I'll give you a hint: this is all about the bending of light. And it's not just light that can get bent as it goes from one medium into another; it can be any kind of wave.

So, let's think about what's going on over here. First, let's think about the part of the pencil that is above the water, so this part right over here. The light is actually reflecting off of this pencil, and then it's bouncing straight into our eye. So, just imagine a path from this dot straight into your eye. Once again, from here it's going straight into your eye.

When we go over here, it still doesn't look too distorted. So, you have light that's going straight to your eye; it's going through the side of the glass and then getting to your eye. But then once we get into the water, something's interesting happens. You would expect the point that what would have been here would then go straight to your eye, just like everything up here.

But it turns out that that light, once it transitions from going from the water to the glass and then the air, it bends. So, at the interface between the media, between those different materials that the light is traveling through, instead of going towards your eye, it gets bent, in this case to our left.

And so, that's why when we look straight on here, we don't see anything in this region right over here. But the light that was going from the pencil towards this part of the glass, which typically you would not see—that would have typically just gone straight in that direction and not hit your eye—well, now that is getting refracted. It's getting bent to the left so that now that light hits your eye.

So, that's why you see what looks like a broken pencil. It's all about the light getting bent as it exits the water and goes into the glass and then the air.

More Articles

View All
Example naming ionic compound
Let’s get some practice naming ionic compounds. I have a formula for an ionic compound right over here, but how would I say this? If you get inspired, pause the video and try to work it out on your own. Well, we could see that it has some magnesium, and …
Michael Burry just sold all his stocks and the reason why is terrifying
So Michael Burry just did something unthinkable in the world of investing: he sold his entire portfolio of stocks. Every single last one! Now, this action is so unconventional that it deserves your attention. As a professional investor working at an inves…
Ruchi Sanghvi Speaks at Female Founders Conference 2015
Good afternoon everyone! I’m so excited to be here today. I don’t think I’ve ever spoken to such a large audience of female entrepreneurs and technologists before. This, I think, we need to give ourselves a huge round of applause! Woo! I’m so inspired by …
Bringing the Meat to Higher Ground | The Great Human Race
Can’t be too greedy right now. In the midday heat of East Africa, lions often retreat to the shade and return to their kill when the sun starts to set. This lion’s gonna come back. I wish we could take the height and everything else. I can’t get it all…
What you should know about microfinance
I want to tell you about micro finance because you might want to either donate to it or get some money from it. I especially want to tell you about Gine America, which is a micro finance bank that I support the most. Micro finance is small loans to people…
Are We At A Turning Point For Crypto? | Crypto Banter
[Music] [Applause] [Music] Oh, it’s a great time to welcome our friend Mr. Wonderful! Welcome back, and Jiren, welcome back to the show. Do you think that we’ve seen the bottom, and is — or are we headed for another leg down? I have a slightly different …