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Learn all about Einstein Photoelectric Effect and Einstein equation on Oscienceworkshop . How he explained Photoelectric Effect and why wave theory failed?  This phenomenon observed by Hertz and performed by Lenard and explained by Einstein. 

Learn Photoelectric Effect 

The Photoelectric Effect - Modern Physics Oscienceworkshop 

Einstein explain when light of particular frequency is incident on a metal surface electron are emitted from it these electron are called photoelectron . The effect is called Photoelectric Effect. 

Einstein Explanation Photoelectric Effect 

• For normal frequency less than threshold frequency no photoelectric effect will occur. 
• No matter for how long light is incident.
• If battery is setup in the photoelectric experiment then electric field will be in the experiment.
• Intensity of light is directly proportional to number of photoelectrons.
• Frequency of light is directly proportional to maximum kinetic energy of electron. 

Observations Made In Experiment 

1. Intensity V's Photocurrent

If frequency is less than threshold frequency no phenomenon will  occur. (See fig below). 

Einstein Photoelectric Effect graph of intensity V's Photocurrent 

2. Photocurrent V's Frequency 

Photocurrent depends on intensity of light and is independent of frequency.

Graph of Photocurrent V's frequency 

3. Photocurrent V's time 

Graph of Photocurrent V's time 

4. Photocurrent V's Voltage 

There are two cases in this observation. 

Case 1 When different intensity 

Case 2 when different frequencies 

Graph of Photocurrent V's Voltage 

Why Wave Theory Failed?

According to wave theory when light incident surface, energy is disturbed continuously over the surface. So that electrons must have a time to travel to accumulate sufficient energy to come out. 

When intensity is increased more energetic electrons should be emitted out . So that stopping potential should be intensity dependent . But it is not observed. 

According to wave theory, if intensity is sufficient then at each frequency electron emission is possible. 

Details Einstein Explanation of Photoelectric Effect 

• Radiation observed by metal are in form of quanta (photon) . Energy of each photon depend on frequency. 
• One photon interact with one electron only and interaction is instantaneous process.
• In the interaction the photon transfer complete energy to the electron.
• The intensity of light is directly proportional to number of photons, hence if intensity increase the number of photons incident increases which deals to more emission of electrons (rise of photons).
• During the interaction the energy and momentum is conserved. 
• All electron from surface has kinetic energy maximum.
• If the frequency of light increases the kinetic energy of photon electron is not same only few electrons have kinetic energy maximum. 
• Number of photons incident is not equal to the number of electrons emitted. 

Graph of Stoping Potential And Frequency

Graph between stopping potential and frequency 

Graph between Kinetic Energy and frequency 

Graph between energy and frequency