Progress of project for the week

Week 1

Research on formation of rainbows.

For the first week of the project, we spent time looking for research articles related to rainbow formations. From what we found, some of the criteria for rainbow formation includes water droplets of sizes between 0.5 to 4mm and a large source of collimated light. In addition to that, the angle of incident light and observer is said to be between 40 to 42 degrees.

Week 2

Proof of concept.

In order to prove the formation of rainbows, we used a sprayer and a projector. However, the light from the projector was not intense enough and we substituted it with a high-intensity torchlight. We were successful in forming rainbows in an outdoor environment. The rainbows formed are roughly 2m in height and the rainbows are partially formed due to the small area being covered by the water droplets and the torchlight

Proof of concept.

Week 3

Design of prototype and down scale of rainbow.

Over the next 2 weeks, we focused on creating a table-top setup to create a small rainbow:

Design of table-top prototype.

Further testing was conducted to see how the ambient light and other factors affect the perceived intensity of the rainbow. We found out that if the background (i.e. behind the rainbow), was too bright, the rainbow would not be easily visible.

Therefore, the insides of the box have to be as dark as possible, so the amount of light absorbed will be maximised. This will help make the rainbow appear more intense since it will be contrasted against a dark background.

With that, we purchased the materials to construct the box.

Week 4

Construction

We could only get our hands on transparent acrylic sheets, therefore we had to improvise in order to make the insides dark. We simply used duct tape to make the insides black. The light source used is the same as before, we used a high intensity torchlight. However the back of the box was too reflective, and the rainbow was either drowned out or not present.

Testing of tabletop set up.

Week 5-6

Back to the drawing board

We manage to observe a rainbow in the box. However, we found out that the “rainbow” that we saw in the box was not an actual rainbow, but instead it was due to the chromatic aberration of the lens on the torchlight, which illuminated the plane of water droplets with the colours of LED lights present.

Projection of colours on the water droplets due to chromatic aberration.

Over these 2 weeks we tried minimizing chromatic aberrations, finding methods to further collimate the incoming light, as we discovered that the more collimated the incoming light, the more intense the rainbow will appear.

A larger box was constructed, with the insides of the box painted with matte black paint.

Formation of rainbow in second prototype with sun as source of light feat. Javier.

Week 7

Testing new light sources

We bought different types of light sources with higher intensities compared to the handheld torchlight.

(Insert new light source pics here)

However, we encountered problems with collimating the light from the new sources. As a result, we were unable to produce any rainbows in this manner. Furthermore, we were told to scale up the rainbow formation to a room-scale setup. Thus, we began searching for a larger light source (e.g., spotlight) and had to design a new prototype to fit the room scale.

Week 8

Testing of spotlights and and preliminary design of final product

We rented a spotlight to test whether it is able to create a room-scale rainbow. Purchasing said spotlights would be out of the question, as the cheapest LED spotlight would cost more than the entire budget that was given to us. The spotlights were subject to availability, and we had to make sure we could rent the most compatible ones for testing and for the final product. We tested the spotlights by using a diffraction grating; the ones with a more continuous spectrum of colours was chosen.

Furthermore, a pump and mister combo will be used instead of a hand-pumped garden sprayer. The use of a pump enables prolonged constant formation of mists required to produce a rainbow.

Testing spectrum of light source.

Testing the capabilities of a spotlight and water pump feat. Azzam & Kelvin.

Formation of rainbow in new setup.

With that, we designed a final prototype.

A black backdrop was rented in order to lower the ambient light around where the rainbow is supposed to form, and to allow for a larger contrast so that the rainbow can look more intense. If a lighter coloured background was used, the rainbow would not be as visible.

We also purchased 6 more nozzles as only 3 pieces were included with the pump. Out of the 6 nozzles purchased, only 2 were authentic nozzles. The other 4 nozzles were from 3rd party sources. We thought that it would not be an issue with forming the rainbow. However, the 3rd party nozzles caused leakages. As a result, the pressure in the pipe dropped causing the water droplets formed to be inconsistent. We had to make do with what we have and we attempted to form the rainbow with only 5 nozzles. The nozzles at the sides of the setup were angled to cover up the gaps.

Final prototype design feat. Kelvin.

Partial formation of rainbows due to a lack of nozzles.

Week 9

Construction of product

Since we will be exhibiting our product at the atrium, inflatable pool  will be used as a water catchment and reservoir, so water could be recycled as much as possible. The spotlight will be positioned approximately 3m above the ground, angled downwards towards the backdrop.

Our final product.

Showcase of our product.

Photo of Azzam behind the rainbow.