Permanent Rainbow

[Phi for All]

I was reading this article about the Kwok brothers in Hong Kong building a full-scale ark as an amusement park/hotel. I don't want to talk about the ark. I don't want to talk about the biblical story. And I don't want to talk about why the Kwok's think it's a good idea to build it in Hong Kong's harbor. What I want to talk about is this:

 

Hong Kong's ark builders also tried to install a permanent rainbow through light refraction but eventually gave up when the science proved too difficult. The Dutch team is also wrestling with the challenge of installing a convincing rainbow.

 

The science proved too difficult?! I knew as soon as I read this that there is a group I know who would take up this challenge.

 

So how would you do it, make a rainbow that could be turned on and off as an attraction at a theme park? Permanent doesn't mean it has to be on 24/7, just that it has to be in a single location and be reproducable at will (OK, just during daylight hours).

[Cap'n Refsmmat]

A water mister and a bright light source in a decent location?

 

Sounds like it could work.

[Sayonara]

I think the incident rays may need to be parallel, which would certainly make for some tricky engineering problems.

[CaptainPanic]

And you want a lamp that gives off roughly equal amounts of light in the entire visible spectrum...

 

And in addition, it has to be one hell of a lamp. The rainbow must be visible, but some thin mist will not even absorb half the light, and it must compete with the Sun! You'll need megawatts in lamps if you want to have a decent size rainbow.

[stereologist]

A water drop based rainbow is too difficult an issue. It would be difficult to illuminate and would not work in poor lighting conditions such as smog or hazy conditions, or cold or dry weather situations. Also, the rainbow would have a rather small area in which it could be properly viewed. A better option would be to illuminate a sheet of material with different lights to form a rainbow pattern. The area of viewing becomes large. Weather conditions such as cold, windy, rainy, hazy weather do not make the rainbow fail.

[iNow]

I wonder if something could be done whereby you surround an area by a glass (or similar material) cube. Have the properties of that cube make it so it looks like a split spectrum to those looking through it, despite the viewing angle. The light source(s) could be within it. Voila... Perma-rainbow. I like this idea because you are no longer requiring air to be your medium, but the glass (or similar) material.

[bascule]

A water mister and a bright light source in a decent location?

 

I was just at the MGM Grand in Las Vegas... they have a "Rainforest Cafe" with a rainbow created using exactly that method.

 

Sorry this picture is so grainy... it was taken on my iPhone which doesn't work so great indoors:

 

 

At the very center of the picture you can kind of make out the rainbow.