A beam of electrons is fired at a crystal of magnesium oxide, and photographic film is used to record the places where the electrons come through the crystal. Which of the following changes to the experiment is not likely to change the interference pattern that results on the film?

increasing the length of time the beam is fired at the crystal

Explanation:

Interference pattern does not depend on duration of the recording, though this might affect clarity of the image on the photographic film. Other things will change where the electrons end up. Speed of electrons affects its momentum, and thus its position. Proton has different mass, so different interference pattern. A different crystal will create a different interference pattern depending on the molecular formula.

there is none because earth is stationary and flat.