Photoemission

Introduction

• Photoemission is a fascinating process in physics where electrons are ejected from a metal surface when exposed to electromagnetic radiation, such as ultraviolet light.

Key Observations

• When a clean, positively charged zinc plate is exposed to intense white light, it will not discharge.
• Similarly, a clean, negatively charged zinc plate exposed to intense white light will not discharge.
• The intensity of light and the charge of the plate do not affect the discharge.

Specific Conditions for Discharge

• A clean, positively charged zinc plate will not discharge when exposed to ultraviolet light.
• However, a clean, negatively charged zinc plate will discharge when exposed to ultraviolet light.
• This indicates that discharge occurs only when the plate is negatively charged, and the source has a high enough frequency (ultraviolet light).

Intensity and Discharge

• The intensity of the source only affects the time it takes for the plate to discharge.

Implications

• Photoemission suggests that light and ultraviolet radiation are composed of individual units called photons.
• For an electron to be removed from a negatively charged plate, each photon must possess sufficient energy to accomplish this.

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Photoemission

Physics

Summary

• Photoemission is the process of ejecting electrons from a metal surface when exposed to electromagnetic radiation.
• It demonstrates that electrons are only ejected when the plate is negatively charged, and the radiation source has a high enough frequency.
• The intensity of the source affects the discharge time, and this phenomenon supports the idea of photons as individual units of light energy.