Physics: 1902

1) Lorentz, Hendrik Antoon

Lorentz, Hendrik Antoon, pronounced LOHR ehnts, HEHN drihk AHN tohn (1853-1928), was a Dutch physicist. He became famous for his electron theory of matter, and shared the 1902 Nobel Prize in physics with Dutch physicist Pieter Zeeman for explaining the effects of magnetism on light.

Lorentz assumed that matter and the ether interact only by means of electrically charged particles. The ether was a medium that Lorentz and other scientists of his day had reason to believe occupied all space. Lorentz's electron theory suggested that moving bodies are shortened in their direction of motion through the ether. This shortening occurs because motion affects forces between the charged particles that make up matter. The change in length actually occurs. It is too small to notice, however, except in precise experiments carried on at very high speeds. The equations that show how motion deforms bodies are called the Lorentz transformations. Lorentz was born at Arnhem, the Netherlands, on July 18, 1853. He graduated from, and taught at, Leiden University. He died on Feb. 4, 1928.

2) Zeeman, Pieter

Zeeman, Pieter, pronounced ZAY mahn, PEE tuhr (1865-1943), a Dutch physicist, became known for his discoveries in spectroscopy, the study and analysis of spectra of light. In 1896, he discovered what is now called the Zeeman effect, the splitting of spectral lines by a magnetic field. The theory for this phenomenon was developed by Hendrik A. Lorentz, and the two scientists shared the 1902 Nobel Prize in physics for their work. Through the Zeeman effect, astronomers measure the strength of the magnetic field on the surface of stars. Zeeman was born on May 25, 1865, in Zonnemaire, in Zeeland, the Netherlands. He died on Oct. 9, 1943.

About Zeeman, effect

Zeeman, effect pronounced ZAY mahn, is an influence that magnetism has on light. The effect changes the color of the light emitted (sent out) by atoms. Scientists can use the light to measure the strength of the magnetism. The Dutch physicist Pieter Zeeman first observed the effect in 1896.

The parts of an atom that actually emit light are negatively charged particles called electrons. An electron emits light when it jumps from a higher energy level to a lower energy level. The color of the light depends on the difference between the levels. The atoms in a substance will emit light when they are given enough energy-for example, by heating the substance.

You can study the light emitted by a particular kind of atom by using a prism to break the light into different colors. The colors appear as bright lines called spectral lines. The Zeeman effect is the splitting of a single spectral line into two or more lines. This effect occurs when a substance emitting light is placed in a magnetic field. A magnetic field is the influence that a magnet or electric current creates in the region around it.

The Zeeman effect occurs because electrons have magnetism resulting from their charge and motion. The effect occurs when the magnetic fields created by electrons of a particular kind of atom interact with the external magnetic field. Depending on how an electron is oriented, this interaction may increase or decrease the electron's energy slightly. Each new energy level makes a different spectral line. In this way, a single spectral line splits into two more lines when atoms are in a magnetic field.