Finding the Speed of Cosmic Rays

From MariachiWiki

                                      The Speed of Cosmic Rays

Date Performed: April 18, 2006

Nicole Alimario

Zubaria Iram

Komal Majahid

Youstina Michael

Abstract

The motive of this experiment is to measure the speed of cosmic rays, using scintillators that detects them, and an oscilloscope that measures them.

Theory

An oscilloscope measures voltage versus time (which appears on the x-axis). The distance is measured between the two scintillators. Thus knowing the distance and the time, we can find the velocity using the equation: velocity= distance/time

Experimental

Materials

4 scintillators

1 oscilloscope

1 measuring tape

2 assistants

Procedure

To determine the speed of cosmic rays, we need distance and time. The distance will be measured between the two scintillators, and the time will be measured from the oscilloscope; the difference between the two waves will tell us the time the cosmic rays take to go over that distance. We will not want to have a small distance between the scintillators because then it will be difficult to read the time difference between the two waves on the oscilloscope. We will start with a certain distance, preferably around 30 cm, and move up gradually to have at least 10 points. By graphing the data as distance vs time, the slope of the best fit line will give us the velocity of cosmic rays.

Data

The table above shows the values we acquired from our experiment and different trials. We recorded four values of time for each distance between the scintillators for increased accuracy. The average of these times was then used to calculate the velocity at each distance. In trial one, the velocity was 7.034 cm/ns. Trial 2, 3, 4, and 5 yielded 7.800 cm/ns, 34.6 cm/ns, 0.8500 cm/ns, and 2.063 cm/ns, respectively.

The graphs I-IV display each individual trial in terms of distance measured, the definative distance therefore the 'x' value, versus time, the estimated (times four) time. Each graph is labeled with a linear line of best fit, most effectively defining the speed of a cosmic ray in terms of mathematical numbers.

The average data table, graph V, is the averaged points of all the time tables, and therefore the most effective estimate of the speed of a cosmic ray. Since the data table is in terms of distance vs. time, simply take the negative reciprocal of the estimated numerical slope to follow in the formula v=d/t (because the way the graph is now, it is represented as t/d).

Conclusion

The table indicated a range of velocities for each point. During the entire experiment, each of us estimated a time for the waves on the oscilloscope, and since all of our time were different was the source of error. The difference in velocities could also be caused by some error in measuring the distance because in the beginning of the lab we were measuring the distance from the middle of one oscilloscope to the middle of the other, and since the measuring tape had to be bent to be read could have caused more error.

Remarks

There was alot of room for error due to each of us having a different time for the same distance, and measuring the distance. What could be done better is if we had used the oscilloscope where both the waves remained still for a longer interval rather than flashing would have helped produce better results for the experiment.