In this experiment, the value of Planck's constant is to be measured using the wavelength of the different colors of the spectra. The theoretical value of Planck's constant is h = 6.626*10^-34 J s, but hopefully the actual value will be very close to that. There are several things that have been done in previous labs that will be used on this lab. The same setup as done with the color and spectra lab using 2 meter and 1 meter sticks to determine the wavelength of a given color. However, this time a different color light is given.
A diode is used in this laboratory which makes sure that the current does not flow in a seperate direction. There were four colors being tested and the voltage was given: red 1.87V, green 2.51V, Blue 2.62V, Yellow 1.89V. Using the equations Energy = charge of electron X voltage, and E= hc/lambda, E = -A/n^2, the wavelengths were calculated. Another measured distance was the distance from the light bulb to the color spectra. These were blue was twenty five centimeters, green 30 cm, red 37.5 cm, yellow 34 cm.
After many algebraic and geometric equations the values of planck's constant were fairly close to the calculated values. Values of 6.53 * 10^-34, 6.36 * 10^-34, and other values close to those values. However, like any other laboratory experiment there are possibilities of uncertainty. No matter how far one can measure something to, there will always be some value of uncertainty.
Human error in this lab is very high because it must be done with two people, making it harder to clarify what one sees. Of course, there is uncertainty in the other measurements as well such as the distance of the length from the LED to the diffraction grating.
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