Low-Energy Electrons: A More Pronounced Wave Nature

1 · Predict

A slow-moving electron has a longer de Broglie wavelength than a fast one. Does this mean a slow electron's wave nature is easier or harder to observe experimentally?

• Easier — a longer wavelength (comparable to atomic spacings or slit sizes) makes diffraction and interference effects more pronounced and detectable.
• Harder to observe for slow electrons.
• Wave effects don't depend on the electron's wavelength.

2 · Set Up

1. Open the slow-electron-wave preset and press Reset. These electrons move much slower than in the electron-de-broglie experiment.
2. Enable the de Broglie wavelength readout.
3. Set the electron's (low) kinetic energy for each trial and record its de Broglie wavelength.

3 · Collect Data

Plot wavelength λ (y-axis) against 1/√K (x-axis) for your three trials. Compare the scale of these wavelengths to the electron-de-broglie experiment's.

4 · Analyze

1. For one trial, compute λ = h/√(2m_eK) using K in the 5-20 eV range. Compare to the table — notice these wavelengths (hundreds of pm) are longer than the higher-energy electron-de-broglie experiment's.
2. Explain why lowering kinetic energy (lowering momentum) always increases the de Broglie wavelength, using λ = h/p.

5 · Extend

1. The 1927 Davisson-Germer experiment scattered slow electrons (similar energies to this experiment, tens of eV) off a nickel crystal and observed a diffraction pattern matching exactly the predicted de Broglie wavelength — the first direct experimental confirmation of matter waves. Explain why slow electrons (with wavelengths comparable to atomic spacing in a crystal) were the right choice for this experiment.
2. Techniques like laser cooling can slow atoms down to extremely low kinetic energies, giving them de Broglie wavelengths large enough to observe striking quantum wave effects (like Bose-Einstein condensates). Explain the general principle connecting 'colder' to 'more wave-like.'

The Physics Behind This Experiment

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