Gustav Kirchhoff

Kirchhoff's current and voltage laws, formulated in 1845, are basic tools for analyzing electrical circuits. They state how current balances at junctions and how voltage sums around closed loops.

Kirchhoff worked with Robert Bunsen in Heidelberg in the late 1850s to connect spectral lines with chemical elements. Their work helped make spectroscopy a method for identifying substances by light.

Kirchhoff showed that a body's ability to emit radiation is linked to its ability to absorb it at the same wavelength. That idea became important for later blackbody radiation research.

Yes. Their spectroscopic work led to the identification of caesium and rubidium in the early 1860s.