Name Atomic Theory Unit The Photoelectric Effect In 1905 Einstein published a landmark paper that exhibited light behaves as a particle called a photon His experiment described the photoelectric effect and is often discussed today to introduce the important interaction between light and matter Using your own laptop or working with a neighbor follow this link to a photoelectric effect simulator http phet colorado edu en simulation photoelectric I Spend some time exploring the simulator What happens when you change the metal The wavelength of light The intensity brightness of the light The voltage of the battery Summarize a few of your findings below Various Changing the metal changes the number and speed of electrons being ejected at different wavelengths of light The wavelength of the light sometimes prevents electrons from being ejected sometimes increases the speed of electrons The intensity of light seems to change the amount of electrons being ejected Changing the voltage changes the speed and or direction of electrons moving across the gap II Exploring the effects of wavelength and intensity 1 Select sodium Set intensity at 25 Set color at blue 455 nm Voltage at 0 00V Press start What do you see A few electrons are ejected across the gap at various speeds 2 What happens when increase intensity Brightness to 50 More electrons are ejected They still move at various speeds 3 What happens when increase intensity to 90 Even more electrons are ejected They still move at various speeds 4 Reduce intensity to 25 Set color at red 700 nm Observation No more electrons are ejected 5 Increase intensity to 50 Observation Still no electrons come off 6 Increase intensity to 90 Observation Still nothing Revised SH 7 7 13 LaBrake Vanden Bout 2013 Name III Exploring the effects of metal identity and wavelength 1 Go back to blue 455 nm Switch metal to zinc Observation No electrons come off 2 Increase wavelength to IR region Observation Nothing happens 3 Decrease wavelength to 280 nm Observation Finally a few electrons are ejected 4 Decrease wavelength to 185 nm Observation Speed of e On average electrons are coming off much faster now IV Summarize 1 Were there any differences or similarities between sodium and zinc in this experiment If so can you describe them Although electrons easily came off sodium at 455 nm no electrons would come off of zinc at this wavelength Still for both metals increasing the wavelengths enough meant that the electrons stopped coming off 2 How did changing the wavelength of light at a constant intensity affect the electrons coming off of the surface of the metal When there were originally no electrons When there were already some electrons being removed When there were originally no electrons coming off the surface of the metal increasing the wavelength still didn t help Decreasing the wavelength enough would cause electrons to start coming off When there were already electrons coming off the surface of the metal increasing the wavelength would sometimes make them stop coming off or at least move more slowly Decreasing the wavelength would cause the electrons to eject faster 3 At a constant wavelength how did increasing the intensity affect the removal of electrons When there were originally no electrons When there were already some electrons being removed When there were originally no electrons increasing the intensity did nothing When there were already electrons present increasing the intensity increased the number of electrons being ejected from the metal Revised SH 7 7 13 LaBrake Vanden Bout 2013
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