HALLWACH'S AND LENARD'S OBSERVATION

• The first thing observed by hallwach's and Lenard's is the photoelectric effect is instantaneous process that means when light falls on metal electron starts emitting instantaneously .
• The second thing observed by Hallwach's and Lenard's is that the photoelectric current is directly proportional to the intensity of light that means when we increase the intensity of light then photoelectric current increase.
• The third thing observed by Hallwach and Lenard is that photoelectric current increase with increase in potential but after a certain voltage  photoelectric current reaches its maximum value and it is called saturation current.
• The interesting thing is that current is not zero even potential is zero and even potential is negative, after a certain negative potential value the photoelectric current becomes zero.
• The negative potential value at which photoelectric current is zero is called cut-off potential or stopping potential.
• The next observation by Hallwach and Lenard is that saturation current is increasing with increase in intensity but cut-off potential is not changing with changing in intensity.
• The last thing observed by Hallwach and Lenard is the saturation current is not changing with frequency but cut-off potential is changing with frequency.