Physics Research Paper
Approximation of Planck’s constant and work function using Photoelectric effect on the particle nature of light
Abstract This experiment aims to demonstrate the particle nature of light by photoelectric effect. Stopping potential was measured against different intensities of yellow (λ = 578 nm) and green (λ = 546 nm) light from first order spectral lines of mercury. No significant relationship was observed for stopping potential and percent transmission. However, charging time was inversely proportional to the percent transmission for the yellow light which implied more photoelectrons were emitted for greater intensity. Stopping potentials for green light was noted to be higher than of yellow light. Ratio of Planck’s constant to electron charge and work function of the photocathode were determined experimentally from the plot of frequency vs. stopping potential from the first and second orders of spectral lines of mercury. The h/e ratio from the plot was 2.345 × 10-15 eV•s with 43.29% error from the literature value and a work function of 0.439 eV. Linear relationship was observed from the plot of stopping potential vs. frequency.
Keywords: photoelectric effect, Planck’s constant, work function, stopping potential
1. Introduction The emission of electrons in a solid surface such as metals when electromagnetic (EM) radiation (e.g. light) hits its surface is called photoelectric effect. This phenomenon was discovered in 1886 by Heinrich Hertz and was investigated further by Wilhelm Hallwachs and Philipp Lenard [1, 2] using a circuit similar to Figure 1. [pic] Figure 1. A circuit for a photoelectric effect experiment. When enough energy is transferred to the electrons in the cathode from the photons on the EM radiation, the electrons maybe ejected from the cathode’s surface and a current is produced. The photoelectric effect can be understood clearly when light is viewed as a
Abstract This experiment aims to demonstrate the particle nature of light by photoelectric effect. Stopping potential was measured against different intensities of yellow (λ = 578 nm) and green (λ = 546 nm) light from first order spectral lines of mercury. No significant relationship was observed for stopping potential and percent transmission. However, charging time was inversely proportional to the percent transmission for the yellow light which implied more photoelectrons were emitted for greater intensity. Stopping potentials for green light was noted to be higher than of yellow light. Ratio of Planck’s constant to electron charge and work function of the photocathode were determined experimentally from the plot of frequency vs. stopping potential from the first and second orders of spectral lines of mercury. The h/e ratio from the plot was 2.345 × 10-15 eV•s with 43.29% error from the literature value and a work function of 0.439 eV. Linear relationship was observed from the plot of stopping potential vs. frequency.
Keywords: photoelectric effect, Planck’s constant, work function, stopping potential
1. Introduction The emission of electrons in a solid surface such as metals when electromagnetic (EM) radiation (e.g. light) hits its surface is called photoelectric effect. This phenomenon was discovered in 1886 by Heinrich Hertz and was investigated further by Wilhelm Hallwachs and Philipp Lenard [1, 2] using a circuit similar to Figure 1. [pic] Figure 1. A circuit for a photoelectric effect experiment. When enough energy is transferred to the electrons in the cathode from the photons on the EM radiation, the electrons maybe ejected from the cathode’s surface and a current is produced. The photoelectric effect can be understood clearly when light is viewed as a
References: 1. H.Young, R. Freedman, and L. Ford, University Physics with Modern Physics, Chapter 38, Pearson Education South Asia Pte. Ltd., Singapore, 2009 2. M. Fowler, The Photoelectric Effect, 3. E. Agra, et. al., Physics 73.1 Manual, Philippine Foundation for Physics, Inc., 2007