Question

PHYSICS: Can someone help me identify a concept/hypothesis and possible experiment to run? THis is supposed to be a mock experiment and not an actual lab completed.

Look around and find a certain pattern. Describe the pattern / phenomena that you have selected. Pretend that you have just performed your observation or observational experiment. You may need to repeat the observation at a later time, if there is a possibility. Illustrate it with a photo or a sketch.

Devise a hypothesis of what created this pattern or what caused this particular pattern/phenomenon. Record it with as much details as possible.

Think of how you can check if your hypothesis is valid (design a testing experiment) and record the prediction of this experiment. It is preferable to provide accurate details of your reasoning , assumptions, and the reasoning behind your prediction. Why you think the suggested cause-effect link would work? Are you making any assumptions? If so, what are they?

Identify what quantities you will be keeping track of and how they will connect the predicted cause to the observed effect. What are these quantities? How would you measure these quantities?

Perform the experiment. If it is possible at all, video-record your experiment to analyze your actions, including the measurements. You have to trust me for now on this, but the more information you get on your thought, work, and measurements, the easier it would be for you to pinpoint the reason for the prediction to be wrong, if that should happen. There is no need in attaching the movie to your submission, but I would recommend you to keep it among the files on Blackboard, so it is within reach if you will need to defend your reasoning.

In one paragraph, explain the results of your experiment. Did they match the prediction?

In the summary, please reflect on the whole process. If the prediction holds true, what would be the better way to further confirm your idea of the cause-effect connection? If not, revise your hypothesis or suggest a different observational/testing experiment to get a better insight into the pattern/phenomenon.

Answer 1

Answer :

• In a low light such as bulb of less watt used in domestic purpose, look towards the source of light with eyes half closed and vision blurred.
• One can see some microscopic objects in a VIBGYOR circular fringe. Those objects look like cells under microscope. Also those are moving patterns and scattered through the fringe. They have definite shape : a non-uniform closed boundary with a dark spot at the center (almost).
• Attach a photo.
• According to my explanation may be this is a multi-slit diffraction pattern on which those moving objects are dust particles. The cause a dark spot is seen may be because it is so close to the eye that we are unable to focus at the actual geometrical boundary of the particle as it is very small.
• A testing kit can be set up to re-perform the experiment.

Instruments required :

1. Number of threads assembled equal to the diameter of human eyelashes Cut them in the length of eyelashes. Align them accordingly as for 1 inch on a non-reflecting surface (any reflecting surface would contribute to the pattern)
2. Source of dim light. Bulb of low wattage will be perfect.
3. Place the source in a way that it can fall on the thread surface from different angles.
4. Any instrument to magnify the pattern. A magnifying glass.
5. A circular rotating surface which will be used to point the light on the threads from different angles.
6. A white paper as a screen at near end.
7. Positioning of arrangement :
   1. Place the rotating surface first on a mount on a table. Any cylindrical objet can serve the purpose. Place the surface on top of that.
   2. Think of any diameter of the circular surface. It is preferable if the disc is calibrated into 360 degrees. The two points touches the perimeter are points A and B.
   3. Near A on the table place the light source.
   4. Near B on the table place the thread surface.
   5. Project the light on the thread surface and look at the pattern.
8. This is the best and simple way it can be verified.
9. The set up at higher accuracy may create some pattern which is not visible with bare eyes, that is it may create pattern sourced from the diffraction through those dust particles.
10. Data to be measured can be:
    1. Radius and length of the threads. At what distance they are apart.
    2. Colours present in the fringe.
    3. Fringe pattern.

Summary:

This whole process can be performed at home with simple apparatus. Instruments used are a low watt bulb, threads with radius equal to the radius of the human eyelash, a rotating surface, a magnifying glass.

Set up the arrangement as described in the process. Now perform the experiment and note down the details you see.