Science Eureka Journey 2011 Term 2 (Day 3)

On Day 3, we carried out the following experiments:
1. Mechanics: Balloon Track!
2. The Strongest Bridge
3. Light Angles: Using Water to Refract Light
4. Suspended Animation (Mass, weight and density)


Experiment 1 was about mechanics. Using simple materials such as balloons, strings and drinking straw, taped together, a fascinating feat is performed. Using a string as a "track", the balloon is made to move along it just by air power. Then, after learning the basics, we competed to build the best "rocket" that was able to travel the greatest distance. This experiment taught us how kinetic energy of the air could allow movement of objects.


Experiment 2 was building a bridge using ice cream sticks. It allowed us to compete between groups to build the strongest bridge. It was tested by hanging weights onto the bridge and noting them. This experiment tested us on both creativity and logical thinking. We figured out that the bridge built with overlapping unit blocks could withstand the greatest force. With this fact in mind and some creativity, our group did very well.


The aim of experiment 3 was to investigate the refraction of light rays in water. Refraction refers to the change of direction of a wave due to change of speed.  A paper clip was placed in a cup. From an angle that we can see the paper clip, we slowly changed the angle in which we were looking from till we cannot see it anymore. After that, water was added while our eyes were looking from the same position. To our surprise, we could see the paper clip after water was added! It seemed the light path has changed! We then learnt that it was due to the refraction of light in water.

The refractive index of water is 1.33

"Refraction is described by Snell's law, which states that the angle of incidence θ₁ is related to the angle of refraction θ₂ by

where v₁ and v₂ are the wave velocities in the respective media, and n₁ and n₂ the refractive indices. In general, the incident wave is partially refracted and partially reflected; the details of this behavior are described by the Fresnel equations."


Water has a higher refraction index than air. As the light is reflected from a denser medium to a less dense medium, the light changes its direction and travels to our eyes.

The theme of experiment 4 is mass, weight and density. Here we got to experiment with the density of different objects. They are water, honey, detergent, pebbles, red beans and Styrofoam.