# Physic

Pages: 2 (294 words) Published: December 4, 2012
Objectives:
To be able to explain how the photoelectric effect experiment works and why a photon model of light is necessary to explain the results. •To study the effect of intensity of light on photoelectric experiment. •To estimate the Planck’s constant, h through the simulation. •To be determine how to calculate the wavelength of light, the work function of the metal, or the stopping potential, if given the other two.

Beginning with the plate made of sodium. Keep all the parameters constant except for the colour (wavelength) of the light and display all the graphs available.

1.Have the light source turned on at very low intensity and battery set to ZERO volts. Vary the wavelength of the light source (from Infra Red to Ultra Violet) until electrons just begin to be ejected from the sodium surface. State the wavelength and note the speed of the electrons. What is the corresponding frequency of the electromagnetic wave? Why is it called threshold frequency?

2.Repeat the instruction 1 above but allow the light to shine on the metal for a longer time before the wavelength is varied. Is your finding different as found in 1? Justify your finding.

3.Repeat the instruction 1 above again but vary the intensity of light this time. Is your finding different as found in 1 and 2?

4.As you shorten the wavelength of the light source, what change did you notice about electron speed? Explain the possible cause of the change.

5.Tabulate the wavelength required to just start a current flow for the 6 available surfaces. (Note: Be sure battery voltage is set to zero.) intensity is set for 5% SurfaceWavelength (nm)SurfaceWavelength (nm)

Sodium491Platinum185
Zinc270Calcium397
Copper248?????312