Question

Describe an experiment which verifies the existence of deBroglie waves

Answer 1

$\huge{\mathfrak{\pink{answer}}}$

⚫Setup of Davisson Germer Experiment:-

The experimental arrangement of Davisson Germer experiment is discussed below:

• An electron gun comprising of a tungsten filament F was coated with barium oxide and heated through a low voltage power supply.

While applying suitable potential difference from a high voltage power supply, the electron gun emits electrons which were again accelerated to a particular velocity.

• In a cylinder perforated with fine holes along its axis, these emitted electrons were made to pass through it, thus producing a fine collimated beam.
• The beam produced from the cylinder is again made to fall on the surface of a nickel crystal. Due to this, the electrons scatter in various directions.
• The beam of electrons produced has a certain amount of intensity which is measured by the electron detector and after it is connected to a sensitive galvanometer (to record the current), it is then moved on a circular scale.
• By moving the detector on the circular scale at different positions that is changing the θ (angle between the incident and the scattered electron beams), the intensity of the scattered electron beam is measured for different values of angle of scattering.

⚫Observations of Davisson Germer experiment:

• From this experiment we can derive the below observations:

• We obtained the variation of the intensity (I) of the scattered electrons by changing the angle of scattering, θ.
• By changing the accelerating potential difference, the accelerated voltage was varied from 44V to 68 V.
• With the intensity (I) of the scattered electron for an accelerating voltage of 54V at a scattering angle θ = 50º, we could see a strong peak in the intensity.
• This peak was the result of constructive interference of the electrons scattered from different layers of the regularly spaced atoms of the crystals.
• With the help of electron diffraction, the wavelength of matter waves was calculated to be 0.165 nm.