Reflection of Light on a Water Tank

Reflection of Light on a Water Tank

I often wondered, since childhood, why after inserting my leg in water it could not appear straight. I also used to question myself the reason why a coin of any denomination when immersed in a water pool appears much bigger than when it is removed from the same pool. Therefore, it is through various laboratory sessions that I was able to find the answer to these questions.

The laboratory exercise is known as “water tank”. We placed a laser beam into the water tank and viewed it from the three different directions including the bottom, the top and the side. This part was quite appealing because I discovered that a light beam would bend when it struck the water tank. Additionally, the light beam was not visible on any point of departure having being reflected, something that aroused my curiosity very much. Stille (2006) points out that due to light refraction (bending), objects placed in water also bend when they cross the light’s interface from the air appearing to have a lesser velocity while inside the water. This proved true with the laser beam and tank exercise. As the light changes upon the interface, thereby making the light wavelength change too then bending seems to occur.

In addition, with the light entering the tank, the wavelength was progressively diminished thus changing the beams direction (Mandelbrot, & Novak, 2004). Therefore, a laser beam may not have the ability to pass into the water entirely as is demonstrated in the experiment whereby the angle of incidence exceeds a forty-one degree angle. This means that, through the process of total internal reflection, the intensity of the refracted rays could not remain constant. The light was transmitted across the boundary of the water tank and as a result, very little was reflected. Thus, the laser beam was continuously reflected at each boundary inside the water tank.

The laboratory exercise was vital since it helped me to understand and get responses to my childhood questions. The exercise was very interesting because I achieved considerable knowledge and learnt many things from the given exercise. Additionally, we varied the experiments with infrared camera and lenses and the results were quite educative.


Mandelbrot, B. B., & Novak, M. M. (2004). Thinking in patterns: Fractals and related

            phenomena in nature. River Edge, NJ: World Scientific.

Stille, D. R. (2006). Manipulating light: Reflection, refraction, and absorption. Minneapolis,

MN: Compass Point Books.

















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