Photoelectric Effect Determining Planck s Constant
Photoelectric Effect: Determining Planck’s Constant
Friday, Section 006
TA: Yilikal Ayino
John Greavu with Daniel Erickson & Kevin Haar
January 31, 2014 PreLab
Up until the eighteenth century, particle theories of light dominated physics, primarily due to the work of Isaac Newton. Thomas Young’s 1805 famous double-slit experiment, which showed that light mimics a wave, extinguished some of these early views. However, in 1887, Heinrich Hertz – who is, coincidentally, perhaps better known for definitively proving the existence of James Maxwell’s and David Hughes’ theorized electromagnetic “light” waves by detecting radio waves around the same time – breathed new fire into the seeming ambiguity. Hertz observed that shining ultraviolet light on electrodes causes electric sparks (electrons being released) more rapidly.
Since light was predominately now thought to just be a wave, three main objections were raised in regard to Hertz’s observation of this now-called photoelectric effect. In 1914, Robert Millikan noticed that there was a cutoff frequency, , at which no more electrons are shot out of the conducting electrodes (this work won him the 1923 Nobel Prize). Other experiments at the time showed that the maximum kinetic energy of the fasted ejected electron, , was independent of the intensity of the light:
Where is the elementary charge and is the “stopping potential” or value of the reversed potential difference (of the apparatus of the photo-electron measuring device) needed to be reached for the current of emitted electrons to be completely ceased. Finally, wave theory also could not explain the lack of any (not absolute, but for all practical purposes) time lag in between light striking the electrode and the emission of an electron.
Albert Einstein won his only Nobel Prize in 1921 for his theoretical contributions to the photoelectric effect. Perhaps taking the work on cavity radiation and energy discreteness of Max Planck more seriously than
Friday, Section 006
TA: Yilikal Ayino
John Greavu with Daniel Erickson & Kevin Haar
January 31, 2014 PreLab
Up until the eighteenth century, particle theories of light dominated physics, primarily due to the work of Isaac Newton. Thomas Young’s 1805 famous double-slit experiment, which showed that light mimics a wave, extinguished some of these early views. However, in 1887, Heinrich Hertz – who is, coincidentally, perhaps better known for definitively proving the existence of James Maxwell’s and David Hughes’ theorized electromagnetic “light” waves by detecting radio waves around the same time – breathed new fire into the seeming ambiguity. Hertz observed that shining ultraviolet light on electrodes causes electric sparks (electrons being released) more rapidly.
Since light was predominately now thought to just be a wave, three main objections were raised in regard to Hertz’s observation of this now-called photoelectric effect. In 1914, Robert Millikan noticed that there was a cutoff frequency, , at which no more electrons are shot out of the conducting electrodes (this work won him the 1923 Nobel Prize). Other experiments at the time showed that the maximum kinetic energy of the fasted ejected electron, , was independent of the intensity of the light:
Where is the elementary charge and is the “stopping potential” or value of the reversed potential difference (of the apparatus of the photo-electron measuring device) needed to be reached for the current of emitted electrons to be completely ceased. Finally, wave theory also could not explain the lack of any (not absolute, but for all practical purposes) time lag in between light striking the electrode and the emission of an electron.
Albert Einstein won his only Nobel Prize in 1921 for his theoretical contributions to the photoelectric effect. Perhaps taking the work on cavity radiation and energy discreteness of Max Planck more seriously than