Quantum Effects and Photons

By the early part of the twentieth century, the wave theory of hght appeared to be well entrenched. But in 1905 the German physicist Albert Einstein (1879-1955 emigrated to the United States in 1933) discovered that he could explain a phenomenon known as the photoelectric effect by postulating that hght had both wave and particle properties. Einstein based this idea on the work of the German physicist Max Planck (1858-1947). 

Max Planck was professor of physics at the University of Berlin when he did this research. He received the Nobel Prize in physics for it in 1918. 

Radiation emitted from the human body and warm objects is mostly infrared, which is detected by burglar alarms, military night-vision scopes, and similar equipment. 

According to Planck, the atoms of the sohd oscillate, or vibrate, with a definite frequency v, depending on the solid. But in order to reproduce the results of experiments on glowing solids, he fonnd it necessary to accept a strange idea. An atom could have only certain energies of vibration, E, those allowed by the formula 

The numbers symbolized by n are called quantum numbers. The vibrational energies of the atoms are said to be quantized that is, the possible energies are limited to certain values. 

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