Shining Light Through a Prism

My question is: What happens when you shine blue, yellow or red light through a prism?

The same as what happens with the white light, with none of the other colours being present.

Try it and tell us. I assure you that the prism will not explode.

"What happens when you shine blue, yellow or red light through a prism?"

The answers are simple:

1) You will understand your homework question.
2) You will understand what JohnDG made very simple with the picture he posted for you.
3) You probably still won't understand why we offer a little help understanding homework but usually refuse to do your homework for you.

If that is not good enough then pick answer "C".

I am not a school child!!!!!!!!!!!!!!

Just want to know the answer to a simple question.

Don't worry. Got it from someone else with some patience.

Sorry for the pun... there are so many freak questions. White light is composite light. A prism separates the wavelengths and they become visible. Each with it's distinctive color. A monochromatic light, a pure light composed of only a single wavelength, does not have any components to break up into. So a pure red light will go in red and come out red.

Thank you so much!

Hi Charlene

I think you meant can the colours combine again,.

Let me redefine your question

If one takes John's diagram but replace the screen with a piece of film with the exact spectrum on it and a white light behind it. If you now put your eye where the light source were.

One of course have to mask out any other rays reaching the eye on a different path.

Would you expect to see white light?

Hullo,

Give us some context, please.

I might answer that the light probably slows down (you didn't say it was already in air), each wavelength slowing down a different amount. But, that might not have anything to do with your question?

It might be that the light doesn't even enter the prism if you exceed the critical angle.

It might be that the prism and the surrounding medium have the same refractive indices for all three wavelengths, and nothing would happen.

So, some context, please? It's another gloomy, snowy day in Pittsburgh and I could probably waste hours and hours giving complicated answers to a simple question.

Old saying" Ask an engineer how much air to put in the tire and he'll tell you how to make a car."

If you read JohnDG's picture from right to left, and line up colored beams in the manner shown, they will combine into white light. (That's a bit oversimplified. The intensities of each must be suitably proportioned, and a small number of beams may not give perfect results. But good enough--we do get pretty decent whites out of color TVs, for instance. Also, the angles in the picture are schematic rather than exact.)

Thank you all. I know very little about science. My question comes from a theory of a spiritual nature. Some say that God is light, and that He devided Himself into smaller portions to create the universe (or us). I want to know what will happen if you take the smaller parts (the colour spectrum) and further devide it. Don't know if my question makes any sence?

Charlene,

That's a difficult question to discuss since you have mixed science and spirituality. This is probably not a good board for religious discussions, but I can address your basic science question. Suppose you have a single color of light (let's say 546.000000 nm green). Depending on the surrounding medium, the prism material, and the angle of incidence, that light will be refracted (bent), or reflected, or changed in propagation speed. But, it will forever remain 546.0000000 nm.

The picture showed seven rays emanating from the prism, but that was just a ROYGBIV schematic. The light is actually already subdivided all along the spectrum. To "run this in reverse" might require the entire spectrum in order to "reassemble" itself into perfect white light. However, a small subset can do a good enough job for many practical purposes, analogous to the aforementioned TV (red, green, blue).

If you put a second prism to the right of the first, upside down, it will reconverge the spectrum into a ray of white light again. The angles in the picture are exaggerated fo illustration. The second prism needs to be close enough to the first to capture all the colors.

Careful, lad, careful.

You really should try that one sometime. It does something unexpected.

I think I see something I may have missed (I thought I was remembering a drawing from before)...but I don't have any prisms on hand to try it out. Now I'm curious to find out my mistake.

It's tricky. Almost every book I've ever seen has it screwed up.You need four prisms to get back to white light. I just looked - even Wiki has it wrong.

I did a little looking around on this too, and found an illustration of two pyramids that purported to diffract and recombine a beam of white light. I'm not sure that it is what I (mis)remembered from before, and I haven't verified it. I wish I had a few collimated light sources and prisms to check it all out.

[Too damned long since I learned anything about optics.]