In a double$-$slit interference experiment, the slits are $0\mathrm{.}20$ mm apart, and the screen is at a distance of $1\mathrm{.}0$ m $.$ The third bright fringe $($not counting the central bright fringe straight ahead from the slit$)$ is $7\mathrm{.}5$ mm from the central fringe. The wavelength of the light used is

A$.300$ nm

B$.250$ nm

C$.750$ nm

D$.500$ nm

E$.375$ nm

The large scattering angles observed when alpha particles were scattered by atoms in a gold foil

A$.$ required that the positive charge and most of the mass of the atom be concentrated in a very small region.

B$.$ were consistent with the idea that the atom has a neutral nucleus.

C$.$ suggested that the positive charges in an atom were uniformly distributed throughout the atom

D$.$ were consistent with all of the negative charge of the atom being concentrated at the center of the atom.

E$.$ suggested that the negative charges in an atom were uniformly distributed throughout the atom.

$1$