A Flat Lens?! / Mr. Denjiro’s Happy Energy! скачать в хорошем качестве

A Flat Lens?! / Mr. Denjiro’s Happy Energy!

DENJIRO: I want you take a good look at my face. BOY: Your face looks so weird! DENJIRO: My face looks big and distorted. I have “Happy Energy” written on this piece of paper here. As you can see, the letters get bigger. That means this transparent board is a lens. But if you look at it from the side… it’s flat and not curved. Usually, a lens is either a convex lens that curves outward, or a concave lens that curves inward. But this is a flat lens. It’s called a Fresnel lens. So why does it have lens-like properties when it’s flat? We can uncover the secret if we zoom in on the lens’s surface. As you can see the surface is jagged. This is key. With a convex lens, the center bulges out. If you slice this up and make it level, you get a Fresnel lens. Basically, the curve is created by the jagged surface. As proof, you can see that on the edge of the lens, the spikes are steep, while at the center, they are shallow. Since a Fresnel lens is a thin lens, you can make light, compact lenses. It can also collect light, like a normal lens. I have here a huge Fresnel lens. I’m going to put it in front of a light source and bring a piece of paper up to it. BOY: It caught fire right away! DENJIRO: It started to burn immediately. A strong light source emits light at a high temperature. But since the energy of light gets diffused, it gets weaker the farther away it is from the source. If you use a lens, you can gather the light that was diffused, and bring it closer to the temperature of the light source. That’s why by gathering strong light or sunlight with the use of a lens, you can create temperatures high enough to burn paper. NARRATOR: A Fresnel lens is often used to make very thin magnifying glasses. DENJIRO: I hope energy will bring you all happiness. Our magic word is "Happy Energy!”