During refraction, what happens to a wave when it travels from one medium to another?
the wave travels in the opposite direction.
the wave changes speed.
the wave moves in the same direction.
the wavelength increases.

Which of the following correctly describes what happens when an atomic bomb explodes? small pieces of fissionable material are joined and form a body with a mass greater than the critical mass, the relative number of neutrons escaping decreases, and a chain reaction and explosion result. large pieces of fissionable matter are brought together quickly and form a body with a mass smaller than the critical mass, the relative number of escaping neutrons increases, and a chain reaction and explosion result.