If electrons were used in the two-slit experiment instead of light, what change would need to be made to the slit spacing in order to see a diffraction pattern?

In order to conduct the two-slit experiment with a beam of electrons, the slit opening has to be smaller than the opening for the light waves. This is because the wavelength of the electron beam is lower, which means it will pass through the large slit without diffracting. Diffraction will occur if the spacing is reduced. The reason that electrons have a smaller wavelength is because they have a higher energy than light waves.

Yes it would be a physical change.

The answer is the first option just took the test