The purpose of this lab activity is to determine planck s constant by measuring the turnon voltage of several leds 1. Shockley equation plot and fit for blue 436nm light. First photoelectric effect apparatus used today showing the mercury light source right and. Introduction lightemitting diodes leds convert electrical energy into light energy. Plancks constant h as the constant of proportionality. Pdf determining of plancks constant using leds researchgate. The goal of our measurement is to give an estimate of the planck constant. Pdf experimental determination of plancks constant using light. Light of a specific frequency f passes through a ring. In this experiment, the above relationship is used to determine plancks constant h. Experimental determination of plancks constant using. Planck s constant is a fundamental physical constant used to describe the energy of a photon. A simple experimental setup for measuring the plancks constant, using landauer quantization of the conductance of touching gold wires, is described.
The emission and absorption of light was an early subject for investigation by the ger man physicist max. Experimental determination of plancks constant h 6. Experimental determination of plancks constant ifscusp. To determine planck s constant h from the stopping voltages measured at different frequencies wavelengths of light. Determination of plancks constant using photo electric. The key parameter for determination of plancks constant using led is the. Experimental physics extrapolation of the bremsstrahlung.
The plancks constant from our experiment was found to be 6. One of the most important experiments from the early 20 th century was the photoelectric effect experiment. The schematic for the circuit used in the experiment. Use an led to give electrons energy aka excitation by electrical means. Two crystals, sodium chloride nacl and lithium fluoride lif, were used in the experiment to provide different bremsstrahlung continuums, with the hope that they could converge on the same value of planck s constant. Read the experiment and answer the following questions.
In the light emitting diodes leds methods, we first make a complete circuit, using various apparatus fig1. The existence of a smallest unit of light energy is one of the foundations of quantum mechanics. This experiment uses a mercury lamp to generate the photons incident on the light sensitive material. Determination of plancks constant using the photoelectric effect mit. Experimental set for measuring the plancks constant using led. The purpose of this lab activity is to determine plancks constant by measuring the turnon voltage of several leds. Plancks constant are concepts that embrace both the chemistry that the physics. In this experiment, you will use light emitting diodes leds to measure. This is a method using leds to estimate planck s constant data book value 6.
Using data obtained through the bombardment of an alkali metal. Determination of plancks constant and work function of. Vicky yumnam 6th semester student of 201617 in theory section a minor mistake. These were placed into the crystal post, standing up with the short edges parallel to the beam path. Millikan made the first measurement of plancks constant in 1916. It consists of two gold wires with thickness of 500 micron and 1.