After reading the book, I was just wondering about the validity of it's claims. The book is probably not correct but i want to know why.
2006-06-30 11:17:14 · 10 answers · asked by Cuban Pete 1 in Science & Mathematics ➔ Physics
You have to change the character of the material to change the refractive index. Also materials can absorb light, which isn't really due to refractive index in the conventional sense of the term. In E&M you can make index of refraction a complex number (a real plus an imaginary component) and use the imaginary part to represent the absorbtive properties.
The refractive index of air is so close to that of vacuum primarily because air is so diffuse. Liquid nitrogen (essentially liquid air) has a much higher index, about that of water. Even liquid helium has a noticible index, and that is not even a dipole!
The invisible man's best bet is to lower his density a LOT. Kinda be hard to function. Can't change index of refraction without also changing the chemistry and/or the density of the material.
2006-06-30 17:31:52 · answer #1 · answered by Mr. Quark 5 · 0⤊ 0⤋
The refractive index of a material is defined to be the ratio of the speed of light in a vacuumm to the speed of light in the material. For example, the speed of light in a vacuum is 300,000,000 meters per second. The speed of light in a typical piece of glass is about 200,000,000 meters per second, so the index of refraction of typical glass is 1.5.
Light bends (changes its direction) as it slows down or speeds up. The amount it bends depends on how much its speed changes and the angle at which it enters or leaves one material going into another. This bending of light, called refraction, is why we can see "clear" materials. Light goes through them, but its motion is affected and we can detect that with our eyes.
In principle, if you could make a clear substance that has an index of refraction identical to the air that surrounds it (about 1.0029), light traveling through the air would pass through this substance without being affected in any way. It would be completely invisible.
The problem with making a human invisible is that humans are not clear. Light reflects off our surfaces. While I don't like saying something is immpossible, it is very unlikely that we will be able to make humans invisible. However, work is being done now on an "invisibility cloak" very much like the one in the Harry Potter stories. The idea is to make a material that will bend the light around the object it covers so the light comes away from the object just as though it had traveled through the object.
The two references listed cover refraction and the invisibility cloak developed in Japan.
2006-06-30 11:33:43 · answer #2 · answered by not_2_worried 2 · 0⤊ 0⤋
Refractive index is the level of Refractivity an object possesses. For example, a mirror has the Refractive Index of about 5.0. Whereas as rock's Refractive index is about .03.
2006-06-30 11:21:52 · answer #3 · answered by Natedogg 2 · 0⤊ 0⤋
Refractive index assumes if the object is already translucent. Actually, you might want to read up on new research on metamateral which deals with invisibility not by light passing through an object but around it like water flowing around a rock in a stream.
2006-06-30 11:33:35 · answer #4 · answered by Anonymous · 0⤊ 0⤋
The refractive index is a constant for a given pair of materials. It can be defined as
speed of light in material 1
speed of light in material 2
This is usually written 1n2 and is the refractive index of material 2 relative to material 1. The incident light is in material 1 and the refracted light is in material 2.
If the incident light is in a vacuum this value is called the absolute refractive index of material 2. This is the value given in data books.
By definition the refractive index of a vacuum is 1. In practice, air makes little difference to the refraction of light with an absolute refractive index of 1.0008, so the value of the absolute refractive index can be used assuming the incident light is in air.
Material Absolute Refractive Index
Air 1.0008
Water 1.330
Glass, soda-lime 1.510
Diamond 2.417
Ruby 1.760
I do not think it can be changed and the invisible man exists only in writer's imaginations.
2006-06-30 11:20:58 · answer #5 · answered by jenssequa 1 · 0⤊ 0⤋
It can be changed and you have seen thousands of examples in everyday life. Eye glasses, especially the new plastic ones have a tune able refractive index by the mix of plastics.
2006-06-30 11:50:08 · answer #6 · answered by satanorsanta 3 · 0⤊ 0⤋
In order for the invisible man to be invisible, he has to have a refactive index of 1, or the same as the air surrounding him.
2006-06-30 16:03:33 · answer #7 · answered by gp4rts 7 · 0⤊ 0⤋
When light passes through something like glass, diamond, etc. It slows down because it is bent by the refraction of the material.
It is basically due to the physical properties of the material and how they affect Maxwell's laws of electromagnetism.
I think this link will help you most:
http://scienceworld.wolfram.com/physics/IndexofRefraction.html
2006-06-30 14:09:44 · answer #8 · answered by cat_lover 4 · 0⤊ 0⤋
It is a constant valve for a material showing how much will that material bend or refract when passing through a medium.
2006-06-30 13:54:23 · answer #9 · answered by Hanna Y 2 · 0⤊ 0⤋
you can't really change the index that easily.
It is doubly difficult to do it with all the different kinds of tissue in human body, esp. if you want it to remain alive.
Finally, if you are passing through all the light, you will not be able to see anything.
2006-06-30 11:25:21 · answer #10 · answered by Anonymous · 0⤊ 0⤋