Final answer:
The Davisson-Germer experiment needs to be enclosed in a vacuum to prevent air molecules from interfering with the electron beam, ensuring the formation of a clear diffraction pattern and accurate results.
Step-by-step explanation:
The Davisson-Germer experiment requires being performed in a vacuum chamber to eliminate the interference of air molecules with the electron beam. When electrons are fired at the crystalline surface in the experiment, diffraction patterns are created which are key to observing and measuring the wave-like behavior of electrons. If the chamber isn't evacuated, air molecules would collide with the electrons, scattering them and thus, preventing the formation of a clear diffraction pattern. This would lead to inaccurate results that cannot confirm the wave nature of electrons as proposed by de Broglie.