Light travels and behaves both as a discrete bundle of photon and wave, which explains how the photoelectric effect of electrons works. The effect can be explained as the injection of electrons from the surface of any mental in response to a given wavelength of light. Rablau et al. (2019) explain that the emission of conduction electrons from metals requires voltage at a short wavelength, such as UV light (visible light).
In this experiment, the velocity of leading the metal surface is studied from a monochromatic light which proves the wavelength of light is matter and not intensity. The experiment exposes the photocathode to monochromatic radiations with a potential applied to the amplifier to oppose the electron energy emitted. The voltage required to stop the current is proportional to the energy emitted; thus, voltage data is obtained and plotted to obtain the stopping voltage allowing the current to reach zero on the meter. After obtaining the stopping voltages, a straight line plot is generated, the slope is used to obtain the Planck’s constant. Einstein energy equation (1) showed the inverse relation between energy and wavelength, which is equated to voltage and work function.
Stopping voltage where it is equal to that of the work function for the electron to be generated;
Plotting a graph against the inverse of the corresponding wavelengths;
The literature planks constant is 6.626 * 10 ^-34 J.s.
The procedure
The Photoelectric effect apparatus was set up on a small stack of books making the aperture opening be 7cm above the table to line up with the mercury lamp.
A digital voltmeter (physics multimeter) was correctly connected to photoelectric effect apparatus using a red and black patch cord. The red patch cord of the photoelectric effect apparatus was connected to the mA outlet of the voltmeter, while the black patch cord was connected to the COM outlet.
A 546 nm filter was placed in front of the aperture on the photoelectric effect apparatus. The mercury lamp was placed directly in front of the opening, and then the lamp was turned on.
The photoelectric effect apparatus was set to zero by adjusting the knop counterclockwise with the current reading near zero while the voltage readings were high. The zero knob was adjusted so that the current meter needle was zero. The voltmeter was turned to near-zero with the current meter still displaying current.
When the highest current reading was attained, the voltage readings were taken after every 0.5 amps, which were achieved by turning the voltage knob until the needle reached the correct number. At this point, voltage readings were recorded. The measurements were taken until the current dropped to zero.
The experiment was repeated while replacing the lamp and filter combination five times. An average voltage at every current reading was obtained.
The filter was changed to 436 nm with a mercury lamp, and the experiment was repeated while re-zeroing the apparatus.
Reference
Rablau, C. I., Ramabadran, U., Book, B., & Cunningham, R. (2019). The photoelectric effect: Project-based undergraduate teaching and learning optics through a modern physics experiment redesign. Fifteenth Conference on Education and Training in Optics and Photonics: ETOP 2019.