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JDK1.0.2 simulations (1996-2001) => Optics => Topic started by: Harbinger on February 17, 2006, 11:46:50 pm

Title: Manufactured Rainbow
Post by: Harbinger on February 17, 2006, 11:46:50 pm
Hi, bear with me. This is a long winded question

I'm aspiring scriptwriter currently in dilema concerning one of my scenes.

I have a character who has to see a rainbow at a certain time in order to
initiate an exchange of dialogue concerning the various myths and legends
of Rainbows. Problem is he has to know that the rainbow was going to be there,
therefore it can't be a freak random occurence of the weather.

I've described a fountain, the centre courtyard piece between a triangle of
towering glass buildings (this fountain doesn't exist. It's purely fictional).
During my research I read that rainbows can occur anywhere where cascading
rain droplets intersect sunlight at the correct angle and the relation to where the observer sees it from.

So my question is can a structure (ie.fountain) be created, using
specifically angled mirrors, that, providing the sun is shining, can create a
rainbow at a specific time of the day, depending on the sun's location.

I want to have a scene where a seat is positioned in front of the fountain
and that every day, At the same time on the dot, providing there's sun shine,
a feint rainbow is can be seen from that seat.

Not being exactly blessed in the knowledge of the physics of science I have no idea
if the season/time of the year effects this in any way.

Another question I have is does it matter if it's a spray or cascading
waterfall fountain? Would that effect the intensity of the rainbow?

Any help would be greatly appreciated.

Title: topic335
Post by: Fu-Kwun Hwang on February 20, 2006, 10:52:58 am
As you can see from the physics of rainbow applet.
If the sun ray is coming horizontally(near sunrise or sunset), you will see rainbow at about 40-42 degree.
If it is one hour earlier than sunset or one hour later than sunrise:
 The angle of sun ray will be  360/24=15 degree, so the rainbow will be observed at 55-57 degree.
So you would not be able to see rainow from the sun ray if it is 3 hours before sunset or 3 hours after sunrise.  (unless you are located at a high place -e.g. on top of a mountain , and looking down).