The Photoelectric Effect

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The Photoelectric Effect

• Chintan Hossain

MIT Junior Lab October 5, 2004
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Outline

• Introduction/Theory
• Experiment Procedure and Data
• Results and Error Analysis
• Conclusion

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Background and Context

• 1895- Heinrich Hertz observed electrons are
  released by UV light
• Energy depends on frequency
• Nature of light Planck showed that Ehv
• Kinetic energy of electrons KEhv-F

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Light Particle or Wave?
Particle
Wave

• Energy distributed continuously
• Light absorbed continuously
• Any amount of energy allowed
• Energy independent of frequency

• Energy bundled into discrete packets
• Light absorbed instantly
• Energy is quantized
• Energy dependent on frequency (Ehv)

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Experimental Apparatus
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Final Results

• Linear fit to e.Vhv F
• h (4.00.3)x10-15 eV.s
• F 1.750.17 eV

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Sources of Error

• Negative anode current (systematic)
• Misalignment of setup in between measurements
  (random)
• Fluctuations in lamp intensity (random)
• Observer bias in determining Vr (systematic)

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Conclusion

• Kinetic energy is linear in frequency Ehv-F
• h (4.00.3)x10-15 eV.s
• Light is made of photons
• Improvements to experiment
• More data points
• Determine functional form of I vs. V
• Improve alignment/focus beam
• Try other metals or frequencies

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Classical Lag Time
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I vs. V for Parallel Plates
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I vs. V for Ring Anode