patterns in nature (physics)

Reflection of light on a water tank

            Since my childhood, I always wondered why my leg does not look straight in water. I also wondered why when putting a penny or a quarter in a pool or a fountain it looks bigger. At this lab, I was able to answer these questions.

The lab exercise is called “water tank”. In this exercise, we shoot a laser beam in to the water tank from three directions. We looked at it from top, bottom, and side. Again the part that interested me was the reason why the beam bends when it hits the water. I immediately got interested in the reason behind the beam not being able to exit the water tank after it is reflected. The reason behind the beam bending is that the light is refracted when it crosses the interface from air into glass so it moves in a slower pace. As stated in the notes, “since the light speed changes at the interface, the wavelength of the light must change, too. The wavelength decreases as the light enters the medium and the light wave changes direction” (Reading 3, waves). The professor also explained it as people trying to go in to a body of water. As soon as they get in they slow down but when they get out they go in a normal pace. Regarding the laser beam not being able to penetrate the water, I found that the anger of the incidence is greater than 41 degree which means that the laser will reflect from glass air back into the glass (reading 3, total internal reflection).

Overall, the lab was very helpful and very interesting. I gained the knowledge that I was looking forward for and was able to learn more. In this lab we also looked at many interesting experiments regarding the infrared camera and lenses.