What principle is responsible for light spreading as it passes through a narrow slit?

When france sneezes, europe catches cold. what did prince metternich mean by this statement? people in france are more likely to get sick than people elsewhere. europeans elsewhere are often inspired by events in france. happenings in france rarely spread across borders. all damaging incidents in europe start in france.

List three reasons why people might be fascinated by something as dangerous as a nuclear weapon.

Restricting immigrants from entering a country may be based on what belief?