What causes the emission of radiant energy that produces characteristic spectral lines for a given element?

When electrons move from a higher energy level to a lower one, photons are emitted, and an emission line can be seen in the spectrum. Absorption lines are seen when electrons absorb photons and move to higher energy levels. ... An atom in its lowest energy level is in the ground state.

he would use the colour black

water at room temperature is flowing through a pipe with pressure taps located 10 ft apart along one section of the pipe, which are connected to a mercury (s=13.6) manometer.