Gold leaf electroscope

• We charge a gold leaf electroscope with a plastic rod

  The charge is accumulated on the surface of the zinc plate and the gold leaf and due to the electrostatic repulsion the gold leaf rises

  
• If we use UV light where photon energy is above the work function electrons are emitted instantly so gold leaf drops

  
  

  If we bring the light source closer and the intensity increases, more electrons are emitted
• If we use visible light no electrons are emitted as photon energy is lower than the work function

  Even if we increase intensity no electrons are emitted due to the 1 to 1 interactions between photons and electrons
• Conclusions

  1. Emission of electrons only depends on the frequency of light not intensity

  2. Electron emission is almost instantaneous

  3. Interactions between photons and electrons are 1 to 1