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==Introduction== | ==Introduction== | ||
Perhaps one of the most well known and frequently used constants of physics both classical and modern, is the speed of light, denoted by a lower case “c”. The speed of light constant is used for many purposes from calculating the distance to astronomical events, to understanding quantum mechanics. In 1972, the accepted value of the speed of light was c=299 792 500(100)m/sec [2]. Today the value for the speed of light is defined as 29.9792 cm/ns. we measured the speed of light using a relatively simple method which involves measuring time delay of an LED pulse using a photomultiplier tube and a Time amplitude converter or simply (TAC). The photomultiplier is a device sensitive enough to measure individual photons. When the cathode of the PMT receives incident photons, photoelectrons are ejected from an anode inside the PMT, [3] the resultant charge pulse intervals from the photoelectrons are then converted into amplitudes by the TAC and displayed on an oscilloscope. The voltage amplitudes can then be converted to time and divided by the distance to obtain the speed of light. This simple, yet effective experiment yielded some exciting results for my partner, Tom and I. | Perhaps one of the most well known and frequently used constants of physics both classical and modern, is the speed of light, denoted by a lower case “c”. The speed of light constant is used for many purposes from calculating the distance to astronomical events, to understanding quantum mechanics. In 1972, the accepted value of the speed of light was c=299 792 500(100)m/sec [2]. Today the value for the speed of light is defined as 29.9792 cm/ns. we measured the speed of light using a relatively simple method which involves measuring time delay of an LED pulse using a photomultiplier tube and a Time amplitude converter or simply (TAC). The photomultiplier is a device sensitive enough to measure individual photons. When the cathode of the PMT receives incident photons, photoelectrons are ejected from an anode inside the PMT, [3] the resultant charge pulse intervals from the photoelectrons are then converted into amplitudes by the TAC and displayed on an oscilloscope. The voltage amplitudes can then be converted to time and divided by the distance to obtain the speed of light. This simple, yet effective experiment yielded some exciting results for my partner, Tom and I. | ||
==Methods== | |||
==Results and Analysis== | |||
Revision as of 13:32, 10 December 2009
Author: Ryan Long
Experimentalists: Ryan Long & Tom Mahony
The University of New Mexico
Department of Physics & Astronomy
email: rlong1@unm.edu
Abstract
The speed of light is a very large value, nevertheless, the speed of light can be measured using relatively simple time of flight methods. Experiments of this sort have been carried out since Isaac Beeckman and Galileo Galilei first tried in the early 1600s. [1] In Junior Lab at University of New Mexico, we measure the speed of light by measuring flight time of LED pulses over the course of a short distance. A major obstacle to overcome in this experiment is the occurence of "time walk", this can cause major systematic error, if not addressed properly. We obtain a value of 29.448 +/- .1424 cm/ns, which is inconsistent with the accepted value of 29.979 cm/ns, indicating some source of systematic error. We discuss possibilities for removing this systematic error in future work.
Introduction
Perhaps one of the most well known and frequently used constants of physics both classical and modern, is the speed of light, denoted by a lower case “c”. The speed of light constant is used for many purposes from calculating the distance to astronomical events, to understanding quantum mechanics. In 1972, the accepted value of the speed of light was c=299 792 500(100)m/sec [2]. Today the value for the speed of light is defined as 29.9792 cm/ns. we measured the speed of light using a relatively simple method which involves measuring time delay of an LED pulse using a photomultiplier tube and a Time amplitude converter or simply (TAC). The photomultiplier is a device sensitive enough to measure individual photons. When the cathode of the PMT receives incident photons, photoelectrons are ejected from an anode inside the PMT, [3] the resultant charge pulse intervals from the photoelectrons are then converted into amplitudes by the TAC and displayed on an oscilloscope. The voltage amplitudes can then be converted to time and divided by the distance to obtain the speed of light. This simple, yet effective experiment yielded some exciting results for my partner, Tom and I.
