# Physics307L:People/Frye/Plank

Steve Koch 04:50, 21 December 2010 (EST):Missing statistical comparison to accepted value / averaging the two orders is not appropriate, given vastly different parent means.

## Plank's Constant

This lab was performed in the junior laboratory in the UNM physics building on November 22nd with Derick Boeck. Following the procedure outlined in Dr. Gold's lab manual

## Procedure and Data

Experiment 1

The lab manual details two experiments for this lab. The first is to measure the stopping potential of both yellow and green light emitted from a mercury lamp. Then we measure the time it takes for the equipment to build to that stable voltage after resetting the charge. We measure the time with different filters placed over the opening. The filters effectively vary the intensity of the incoming light. The filters are labeled as 100%, 80%, 60%, 40%, and 20%. By measuring the time it takes for each intensity to build to the stopping potential, we hope to establish a relationship between that time and the intensity. The idea is that if the particle theory of light is true then the stopping potential will be the same for each intensity, but the time will increase as the intensity decreases.

Experiment 2

The second experiment is to measure the stopping potential of different wavelengths of light in order to find a relationship between the frequency of light and the energy of a photon. We then will use this data to calculate Plank's constant (h). Plank theorized a relationship between the energy of a photon and it's frequency. E=v*h where E can be calculated from the stopping potential in our experiment, and the frequency v is calculated from the known wavelengths of the mercury spectrum.

Our data and analysis: Image:PlanksconstantFRYE.xls

## Results

I calculated Plank's constant to be:

h = 7.61(39)*10^(-34) (kg*m^2)/s