Planck’s Constant Apparatus

The Planck’s Constant Apparatus is a precise laboratory instrument designed to demonstrate and measure Planck’s constant via the photoelectric effect. It typically includes a vacuum photo tube, a halogen tungsten light source, a set of color filters for varying light wavelength, regulated DC power supplies, and sensitive digital meters for current and voltage measurements.

Key Components

Vacuum Photo Tube: The sensitive device where photoelectrons are emitted upon light exposure.

Light Source: Usually a 12V/35W halogen tungsten lamp, providing adjustable light intensity.

Optical Bench: A rail system allowing adjustment of the distance between the light source and the phototube.

Color Filters: Different filters (red, yellow, green, blue, violet) that select specific wavelengths for analysis.

Digital Voltmeter and Nanoammeter: For precise measurement of stopping voltage and photoelectric current.

Voltage Controls: Potentiometers and polarity switches to carefully adjust accelerating voltage applied to the tube.

Light Intensity Control: Adjusts the intensity of light falling on the photo tube for controlled experiments.

Purpose and Usage

Enables experimental determination of Planck’s constant by measuring stopping voltages across different wavelengths.

Demonstrates the photoelectric effect, showing the relationship between light energy and electron emission.

Provides a hands-on practical tool for higher education physics labs teaching fundamental quantum mechanics concepts.

Typically supplemented with detailed instruction manuals, calibration controls, and safety features.

This apparatus provides a robust educational platform to explore one of physics’ foundational constants with accuracy and clarity.