Arnav Prasanna, a student at Candor International School, describes his experience attending “PriSM 09: Getting Personal with Rainbows” at ICTS.
Thanks to Kritika Srinivasan, my counsellor who introduced me to this workshop that is happening in ICTS campus in Bangalore. I found this topic to be interesting and given its hands-on activity, I wanted to attend. So, my dad and I drove 60kms from Electronic City to ICTS campus to attend this workshop and explore the beautiful campus.
Who doesn’t love a good Rainbow deep dive!
After driving for more than 90 minutes, I was surprised by how silent the campus felt. It was not how I had imagined it. As I commented on the silence, my father explained that this is what a deep science learning environment feels like. Here you have thinkers, and thinkers need open spaces, silence to do their work. We found that there are chalkboards everywhere in the campus, and a lot of formulas written on them.
I felt like I was entering into the brain of Einstein and I was not just learning science from a textbook, I was stepping into the world where science is actually created.
As the workshop started, we began indoors in small groups of three. Kaushik Basu, a science instructor from UC Berkeley guided us on the concepts. On each table there was a glass beaker filled with water, a green laser pointer, and a sheet of cardstock. Our first task was to observe how light behaves when it passes from air into water and back into air again.
When we shone the laser into the beaker, I observed three important phenomena, refraction, internal reflection and refraction again.
I learnt the concept of Angle of Deviation. For our class, the average deviation angle for the green laser was approximately 42.65 degrees. Kaushik Basu explained that this number is very close to the angle associated with natural rainbows.
While I knew about reflection and refraction, the concept of total internal reflection was a fascinating concept I got introduced to for the first time.
That was the moment I understood how fibre optics works and how we get fast internet at home, thanks to how light carries information across the world.
Listening to Neil deGrasse Tyson speak about astrophysics, I often hear about light bending near massive objects in space. Seeing light bend inside a simple glass beaker made me realize that the same laws of physics operate everywhere, right from my classroom experiment to distant galaxies.
Modelling a Rainbow Outdoors
Next, as a team we folded the cardboard into a triangular shape and tilted the entire setup. This allowed us to simulate different positions of the Sun in the sky. It was fun to understand that when the Sun is low in the sky, the rainbow appears high and when the Sun is high, the rainbow appears low.
This explains why rainbows are most commonly seen in the early morning or late afternoon.
Measuring the Rainbow Angle in Real Life
The most fun part of the workshop was us stepping into the sun and modelling rainbows. We were given a water sprayer and guided on how to generate a rainbow and make observations. We used a homemade inclinometer made of a protractor, a viewing straw attached along the flat edge and a string with a small weight to indicate angle measurement.
First, we measured the angle of the Sun by aligning the straw with our shadow. For our group, this angle was about 45 degrees.
Next, we used a spray bottle to create fine mist in front of a black chart paper. When sunlight passed through the mist, a small rainbow formed.
Although our group’s numbers were slightly lower than expected, the typical deviation angle for rainbow light is around 40–42 degrees, which closely matches the value and our earlier laser experiment. What surprised me was how closely our measurements matched the theoretical value. It felt like we were uncovering a hidden rule of nature.
This workshop did not just teach me how rainbows form. It made me realize that understanding the universe begins with understanding simple phenomena around us. If light behaves with such precision inside a tiny water droplet, I began to wonder how it behaves near stars, galaxies, and black holes.
I now look forward to attending more workshops like this, where simple experiments can open doors to bigger questions about the universe.