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Light always travels at "the speed of light" in a vacuum, i.e. when it isn't hitting many particles. When it enters the prism, it hits a lot of particles of glass and therefore gets effectively slowed down. (The exact mechanism is complicated.) When it gets back into the air, it isn't hitting nearly as many particles, so it goes fast again.One of the effects of the glass is that is that different wavelengths of the light slow down different amounts. Different wavelengths correspond to different colors, so different colors travel at different speeds in the prism. The colors get separated because the way light bends at the surface depends on its speed, so different colors have different speeds in the glass, and get bent into different directions.
The apparent problem involved with "speeding up" is not really a problem. Light has no mass so you don't have to give it a push for it to speed up when it is back in air.
I read somewhere that when light travels through a medium, it is infact being absorbed by the atoms of the medium and re-emitted by them right away, in effect passing the light beam down a chain of atoms until it reaches the end of the medium and re-enters the air/vacuum/whatever. If this is the case, when the light is re-emitted by the final set of atoms, it will be re-emitted at the speed of light and hence continue at the speed of light.That's my theory, if someone could confirm or deny this that' be great.Jon
Light is a wave motion in which proagating energy is oscill;ating between two different forms of energy storage. the propagation velocity of all wave motions is deopenant on the "elasticity" of the medium only and changes in either direction as the medium changes.It is possiblr to partially recombine the split light backinto white light with a prism in the reverse sense. This is the way achromatic lenses are made.The expression prism refers to the shape of a rod with a triangular cross section.
Neilep, I will try to explain what I mean, and looking around on the internet sources point to me being correct.When light hits a transparent medium such as glass, the energy from the light photons excite electrons in the medium which jump up to higher energy levels. These electrons then jump back down to their original energy levels and re-emit the light as a photon with the same properties as first which carries on until it meets another electron. This will continue to happen until the light has seemingly passed right through the medium unobstructed. The light infact travels between the atoms of the medium at the speed of light - it is the changing energy states of the electrons that introduce a delay and cause transmission to slow. Hence, when the energy is released as a photon by the final atom in the chain, it will continue it's journey at the speed of light, as it did between atoms in the material.It is worth noting that most transparent materials contain impurities so not all light shined at a piece of glass will pass through. Some will either be reflected or completely absorbed.Colour filters work because the mix of materials used to make them will absorb all frequencies of light other than the intended colour, which will be transmitted through the medium in the way mentioned above.Hope this helps!Jon
Can a glass prism separate radiowaves as it separates light into seven colours? Is it true that a glass prism separates sunlight into 9 colours (7 visible and 2 invisible}?
Quote from: labview1958 on 13/08/2009 10:42:36Can a glass prism separate radiowaves as it separates light into seven colours? Is it true that a glass prism separates sunlight into 9 colours (7 visible and 2 invisible}?A glass can separate radiowaves extremely little, because glass' refractive index at those frequencies is extremely low.
If the light is absorbed by the atoms in the prism, shifting electrons to a higher energy level, then being re-emitted as the electron returns to its original energy level, why does the light continue in the same direction? Why isn't it re-emitted in a completely random direction?
I see. So what krytie75 was saying is incorrect?
Is it possible that light becomes heavier thus slows down in glass? E=mc2. Thus increase in mass slows the speed to keep E constant?