Notes on Hertz’s Observations - Photo Electric Effect - Dual Nature of Radiation and Matter

Notes on Hertz’s Observations - Photo Electric Effect - Dual Nature of Radiation and Matter

Definition of Photoelectric Effect:  

The emission of electrons from a metal surface when exposed to light of suitable frequency.

Hertz’s Observations Working Setup

1. Transmitter (Spark Gap Source):  

Induction coil produced high voltage.  

Plates P₁, P₂ connected to metallic spheres S₁, S₂.  

Sparks across S₁–S₂ generated electromagnetic waves.  

2. Receiver (Detector):  

Wire loop with spheres S₁′, S₂′ separated by a small gap.  

Incoming electromagnetic waves induced a potential difference, causing sparks across the gap.  

3. Illumination Effect:  

When detector was illuminated with ultraviolet (UV) light, sparks across S₁′–S₂′ occurred more easily.  

UV light helped electrons escape from metallic surfaces, making the gap more conductive.  

Observation : 

Sparks in the detector gap were stronger and more frequent under UV light.  

Light directly influenced electron emission from metals.  

📝 Conclusion

Illumination with light increases the sensitivity of the spark gap device.  

UV radiation causes emission of electrons from metallic surfaces.  

This was the first evidence of the photoelectric effect.  

🌟 Significance : 

Hertz’s experiment showed that light can release electrons.  

It laid the foundation for later work by Hallwachs, Lenard, and Einstein.  

Crucial step toward the quantum theory of light.