Two Features of the Photo-Electric Effect

The photo electric effect, which was first documented by Einstein in

1905, and posited that the energy of liberated electrons is linearly

dependent on the frequency of incident photons. This paper

investigates this relationship and measures Planck's constant

($4.36pm 0.04e{-21}$MeVs), and the work function of the photo diode

($-1.52pm0.02$V). Another phenomena which is checked is the charging time

of the stopping potential voltage. While there was some dependence

between stopping voltage and intensity, this effect is mostly

systematic. Both of these experiments provide evidence that the

energy imparted by incident photons is dependent on the frequency, and

the number of photo electrons is dependent on the number of incident

photons.

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section{Introduction}

label{intro}

The photo electric effect describes the energy required to liberate an

electron from a material given an incident photon. These freed

electrons are called photo-electrons. This effect was first

documented by Einstein in his famous 1905 paper for which he one the

Nobel prize in 1921.

While Einstein's original formulation didn't explicitly refer to

Planck's constant, the traditional formulation of this relationship

iscite{klassen}:

egin{equation}

h u = eV + W_o

end{equation}

Where the left hand side describes the incident photon, and the right

hand side describes the energy of the liberated electron plus the work

function of the atom. In this formulation, as well as what is measured

in the lab, $V$ represents the retarding voltage required to stop the

liberated photo-electr...

... middle of paper ...

...requency of the monochromatic light is

what ultimately characterizes the energy of the photo-electrons.

This paper investigated two features of the photo-electric effect.

The first was the linear dependence of frequency on photo electron

energy. This allowed us to measure Planck's constant ($4.36pm

0.04e{-21}$ MeVs), as well as the work function of the photo diode

($-1.52pm0.02$V). The second experiment investigated the effect that

the intensity of the incident beam had on charging time. The

observations of both of these experiments support a model of light in

which the energy of monochromatic photons is dependent on the

frequency and not on the intensity of the incident photons. The

longer charging times at lower intensities supports the theory that

the number of photo-electrons produced is dependent on the number

density of incident photons.