# Will, Red, Green and blue lasers wen crossed create the spectrum we crossed ?

1. Jul 26, 2012

### JD1

will, Red, Green and blue lasers wen crossed create the spectrum we crossed ??

hia,

if i get red, green and blue lasers, and cross them at one point, and change the intensity of each one accordingly, will at the point of where they cross, display different colours relevant to the mixture of said lasers, ??

Thank you

2. Jul 26, 2012

### tiny-tim

hia JD!!

yes, if you put a piece of paper where they cross, you will see white, or any other colour, the same as if they were separate dots on a photo or a tv screen

it has nothing to do with physics, it's just the way the human eye works

there are still only three wavelengths present, ie three different colours, but we see them as one colour, same as on a photo or tv screen

(if we had eye cells for each frequency, same as the ear has, then we would still see three colours!)

3. Jul 26, 2012

### JD1

Re: will, Red, Green and blue lasers wen crossed create the spectrum we crossed ??

so if they were to cross in mid air, at that point of crossing, they wouldn't display the appropriate colour, they would have to hit something ? :-)

4. Jul 26, 2012

### tiny-tim

yes, since there's no physical change, there has to be something for a human eye to see for the effect to appear

5. Jul 26, 2012

### JD1

Re: will, Red, Green and blue lasers wen crossed create the spectrum we crossed ??

i see, so if a given space, however big by so big, was occupied with say a transparent gaseous material, would this suffice ?? :-)

6. Jul 26, 2012

### tiny-tim

?? if you mean a gas, then say so!!

(why use almost 30 letters when 3 will do?)

if you can't see the gas, then you can't see any colours either

7. Jul 26, 2012

### Drakkith

Staff Emeritus
Re: will, Red, Green and blue lasers wen crossed create the spectrum we crossed ??

If the gas was transparent, then you cannot see the lasers, as the light must bounce or scatter off of something and make its way into your eye. If you simply point the lasers at a single spot on a surface, such as a piece of paper, you can see the different colors they produce as you change the intensities of each. You could also fill a transparent container with something like fog or smoke and get a similar effect.

8. Jul 26, 2012

### JD1

Re: will, Red, Green and blue lasers wen crossed create the spectrum we crossed ??

Thank you both, :-)