THE PHOTOELECTRIC APPARATUS USING LEDs AS LIGHT SOURCES

• Main Author: (NIM 20207075), RISDIYANTO
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/12580
• Institution: Institut Teknologi Bandung

The photoelectric effect is studied in high school physics and elementary physics courses. We have created an inexpensive and simple apparatus for this experiment. The apparatus is composed of voltage regulator circuit, light source, vacuum phototube 1P39, and current amplifier circuit. LED light source using a variety of colors. The LED intensity can be varied by changing resistor in series with it. The 1P39 vacuum phototube is very sensitive to light from 400 nm to 700 nm. The current amplifier circuit is consists of two opamp CA3140E and TL081CN as current to voltage converter and voltage amplifier respectively. The apparatus allow us to perform photoelectric effect experiment without a nanoammeter because the low current has been converted to voltage. The experiment using this apparatus shows us the dependency of photocurrent to light intensity, the dependency of photoelectron kinetic energy to incident light wavelengths and independency of photoelectron kinetic energy to incident light wavelengths. The photocurrent increases with the incident light intensity but the stopping voltage does not. Another experiment can be performed with this apparatus is to measure Plack’s constant and work function of electrode. Our measurement to Planck’s constant is 15% below the accepted value. Our measurement to work function is 4% below the value provided by literature.