Answer 1: The partially submerged pencil looks different from different views. From the top, the pencil appears straight and normal albeit with one half of it submerged in water. From the side, the story is different. First, the part of the pencil submerged in water appears to be thicker than the part of the pencil in the air. Second, there is an apparent discontinuity in the pencil at the air-water boundary. The part of the pencil underwater and the part of the pencil in the air do not meet at this boundary. When you look at the pencil diagonally downwards from the side, the pencil is continuous but it appears bent at the air-water boundary. Moreover, I can simultaneously see two pencils – one through the top of the water and the thicker disjoint pencil bottom through the sides of the glass.
For the CD exercise, I used a strong white LED flash from a cell phone as the light source. What I saw was patterns of color in the surface of the CD with the color patterns matching those of a rainbow. The patterns formed some kind of a bow emanating from the center of the disc away from the LED flash light. The patterns also moved around as I changed the orientation between me, the disc and the LED lamp.
One modification I tried was to use another light source – a computer screen. I made a large black picture in MS Paint and added a tiny white square in the middle approximately 1.5cm in the side. When viewed at full screen, the small white acts like a small lamp. The same patterns also appeared but what is different was that the colors are not continuous. Instead of a continuous blend of colors from red to violet, I only saw discrete colors. In fact, I can identify five distinct squares of color in the surface of the disc. These colors are red, orange, yellow-green, blue green and violet.
Answer 2: I think that this experiment is related to the colors of the sky. Red and Blue are the two colors of the sky depending on the time of day with the sky being blue most of the time and appearing crimson during dusk and dawn. Although in this experiment, it is the angle of the view of the light source which is varied, I am taking a stab to say that it is not the angle of the light source which is causing the shift but rather it is the thickness of the milky water which contributes to the color. Viewing the light from the sides means that the light passes through less milky water as compared to viewing it from the top. This can be analogous to the sky. When it is noon, the sun’s rays are passing through a thinner amount of atmosphere. This is also the time when the sky is blue. When the sun is near the horizon, it passes through a thicker layer of atmosphere because it is coming from the side. This is also the time that the sky appears ruddy.
Answer 3: I think that the performance of the CD experiment in this case was very thorough as the experimenter took note of exactly how the spectrum moved as the disc is moved. The attention to detail also reaches the careful note taking on the order of colors. The same can be said for the pencil experiment as the experimenter also took great care in creating an ordered exploration of the views of the pencil. The rotation of the glass was just great as it allowed the experimenter to not only see the pencil from all angles but to also see any trends which may develop as the glass is rotated.
Hewitt, P (2005). Conceptual Physics 10th Edition. New York: Addison Wesley.