Welcome to the Physics Magic Show. My first trick, I'm going to need a volunteer. I choose yellow. Why don't you come up here and join me, sir. Okay, nice to meet you. What's your name? Prano. Everybody, Prano! Anyway, anyway, anyway. Got new money. Yeah, I have a bus. Look at this kid, he's loaded. Okay, here. So we're going to take his cleaning crisp $5 bill. And I'm going to hold it once. Voice into fourths. Now, I'm going to put this bill on top of my trusty old black box. And take this clear glass cup and put it right on top of the bill. Okay, so now we're going to take a cup of water. I'm going to fill up this cup. Voila, the bill disappeared. What'd you do to my money? Don't worry, sir. I got this. Okay, if you didn't notice, this whole setup was on top of a box. But this is no ordinary box. It's a really special box. If you look at the box right now, you can see that it's completely empty. But if we were to do a little bit of magic, Voila, you can see that the bill has reappear. Alright, let's go ahead and take out the bill. Okay, so what do we have here? Here we go. And that's magic. Hey, where am I at? Four dollars. A magician never fails his secrets. Okay, so for the first experiment. So what we have here are the glass cup and the bill. When the glass is empty, the white bends slightly at the glass air barriers. However, these bends are essentially cancelled out and the bill still appears at the bottom of the glass. When the glass is full of water, the glass water barriers bend the light so that when it reaches the final glass air barrier, it is at an angle greater than 48.6 degrees, the critical angle of glass. Because of this, the light is totally internally reflected and the camera sees none of the bill. So what we have in the second part of the trip with the box is a false button. So when we take the bottom out, we see that the light from the observer is being reflected on to a mirror, placed 45 degrees inside the box, onto the bottom of the box. So that's how we can see the bill. The mirror inside the box is a plane mirror. Because it is placed at 45 degrees, when the bill is reflected from flat on the bottom of the box, it appears upright on the back of the box. Thanks for watching! .