1 00:00:00,000 --> 00:00:09,000 Hi. I'm Michelle Shin. Welcome to the Department of Energy's Jefferson Lab. 2 00:00:09,000 --> 00:00:13,000 Hi, Dr. Shin. This is a neat looking place. What do you do here? 3 00:00:13,000 --> 00:00:20,000 Well, I'm a laser physicist. That's a scientist who studies and makes different kinds of lasers and uses them to hit different objects. 4 00:00:20,000 --> 00:00:23,000 Lasers? Like in Star Wars? 5 00:00:23,000 --> 00:00:27,000 Well, sort of like that. So anyway, what can I help you with today? 6 00:00:27,000 --> 00:00:31,000 We were using mirrors this morning and noticed that light bounced around the room. 7 00:00:31,000 --> 00:00:34,000 We want to know more about how light bounces. 8 00:00:34,000 --> 00:00:37,000 Well, I'd be happy to answer that for you, Bianca. 9 00:00:37,000 --> 00:00:44,000 Light that bounces off a surface is called reflective light. The type of surface determines the kind of reflection you get. 10 00:00:44,000 --> 00:00:47,000 A mirror is really shiny. Does that make a difference? 11 00:00:47,000 --> 00:00:53,000 It makes a big difference. If the surface is shiny, then the image you see looks just like the object. 12 00:00:53,000 --> 00:00:57,000 So a surface that is not shiny and smooth will scatter light? 13 00:00:57,000 --> 00:00:59,000 That's right. You catch on really fast. 14 00:00:59,000 --> 00:01:01,000 Does light only reflect? 15 00:01:01,000 --> 00:01:03,000 No. Light also refracts. 16 00:01:03,000 --> 00:01:05,000 What does refractive mean? 17 00:01:05,000 --> 00:01:08,000 Well, Bianca, I think it's easiest to show you. 18 00:01:08,000 --> 00:01:13,000 Okay, Bianca, we need to put on some gloves and goggles because you're going to work with some liquid nitrogen. 19 00:01:13,000 --> 00:01:14,000 We use these in science. 20 00:01:14,000 --> 00:01:17,000 Good. It helps to be safe when you're doing experiments. 21 00:01:17,000 --> 00:01:19,000 What's that stuff bubbling? 22 00:01:19,000 --> 00:01:24,000 It's liquid nitrogen. We're going to use the vapor to explore reflection and refraction. 23 00:01:24,000 --> 00:01:27,000 So, Bianca, this is a laser, and I'm going to shine it on the gelatin. 24 00:01:27,000 --> 00:01:29,000 But first, I need to have you dim the lights. 25 00:01:32,000 --> 00:01:36,000 What I'm going to do now is shine it on the gelatin. Look closely and tell me what you see. 26 00:01:36,000 --> 00:01:40,000 I see the light coming up into the gelatin. That must be reflection. 27 00:01:40,000 --> 00:01:41,000 Right. 28 00:01:41,000 --> 00:01:43,000 But the light is also being bent. Why is that? 29 00:01:44,000 --> 00:01:52,000 Well, when light travels from one medium, such as air, to another medium, such as gelatin, its speed changes. 30 00:01:52,000 --> 00:01:57,000 And when the speed changes, the light bends, and we call that light refraction. 31 00:01:57,000 --> 00:02:01,000 Does the speed of light speed up or slow down when it's going through the gelatin? 32 00:02:01,000 --> 00:02:04,000 Well, because the gelatin is thicker than air, it slows down. 33 00:02:04,000 --> 00:02:08,000 I wonder if magicians create some of their magic with mirrors. 34 00:02:08,000 --> 00:02:15,000 This is a concave mirror. It curves inwards, and you can see that your image, if I hold it in one way, is upright. 35 00:02:15,000 --> 00:02:18,000 And as I get closer, it gets inverted. It turns upside down. 36 00:02:18,000 --> 00:02:21,000 That would be an easy way to stand on your head. 37 00:02:21,000 --> 00:02:22,000 It really would. 38 00:02:22,000 --> 00:02:27,000 This is a convex lens. You can see that the surface curves outwards. 39 00:02:27,000 --> 00:02:30,000 And as you look at it, you look much smaller. 40 00:02:30,000 --> 00:02:34,000 And another place that uses lenses and mirrors is NASA. 41 00:02:34,000 --> 00:02:37,000 NASA needs mirrors and lenses for their big telescopes. 42 00:02:37,000 --> 00:02:46,000 Space telescopes like the Hubble Telescope or the Mars Global Surveyor or the GOES weather satellites. 43 00:02:46,000 --> 00:02:50,000 That's cool. Thanks, Dr. Shin. Bye.