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Stopping Voltage in Photoelectric Effect


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I don't know what sort of apparatus you are talking about, but I recently learned about the photoelectric effect.

Photoelectric Effect - many metals emit electrons when light (electromagnetic radiation) is shined on them. The photoelectric effect is an instance where electromagnetic radiation behaves like a particle (called "photon") rather than a wave.

Waves vary in both frequency and amplitude. However, the energy (E) carried by each individual photon of a wave is determined by the wave's frequency (υ), not its amplitude.

E = hυ

(h is planck's constant)

For the photoelectric effect to occur, each individual photon must have enough energy to dislodge an electron, thus the wave must have a high enough frequency. However, different metals have different threshold frequencies.

Edited by Mondays Assignment: Die
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Thanks for the insight. I am actually referring to the device used here





I understand the mechanics and theory of the photoelectric effect but never heard of Stopping Voltage. So I just wanted some clarification about its purpose and why it is important to calculate it.

Edited by blazinfury
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The stopping voltage where the current goes to zero is proportional to the KE of the electron.


[math] h\nu = E_I + KE[/math]


Simply detecting a photocurrent doesn't tell you the electron's energy. You could try and find the photon energy where the PEE just barely works, but what if you don't have a continuously-tunable light source? (which most people don't). But a retarding potential is easily tuned.

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