Class 12 Physics Dual Nature Radiation Matter Davisson and Germer Experiment

Davisson and Germer Experiment:

  • Davisson and Germer experiment showed the wave nature of electron for the first time
  • They studied the diffraction effects of electron in crystal diffraction experiment
  • The experimental setup for the experiment is shown below:

The experimental setup consists of:

  • Evacuated chamberfor the free movement of electron without any air resistance
  • Electron gunfor the emission of electron
  • BatteryUsed for the acceleration of electrons inside the cylinder
  • Cylinder with fine hole along its axisconnected to the battery so that electrons entering it could be accelerated to high speed
  • Nickel Targetused to deflect electron beam towards the detector
  • Movable detector(collector)to detect the intensity and scattering of electrons deflected by the nickel crystal at varying voltage supplies(44 to 68 V)
  • Galvanometerto measure the small values of current

Observations:

  • Strong peak was detected at 55V, and the angle of scattering was observed to be 50°
  • The pattern of deflected electrons was quite similar to the diffraction pattern of waves
  • The wavelength corresponding to the electron (matter wave) was found to be λ = 0.165nm
  • The experiment was in strong agreement with De Broglie’s hypothesis

According to De Broglie’s hypothesis, matter wave is given by:

 

  • The experiment proved that electrons behave as a wave under specific conditions as the scattering of electron gave rise to the diffraction pattern

On putting the value of V= 55V (the value at which a strong peak was detected), we get

The wavelength calculated above using De Broglie’s hypothesis is equal to the wavelength observed in the Davisson and Germer experiment. So, Davisson and Germer experiment was consistent with De Broglie’s hypothesis.

 

  • Hence, this experiment proved that electron behaves as a wave under specific conditions.

 

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