Particle theory of light

The wave theory for light provides a satisfactory explanation for these observations. It was, indeed, this very experiment conducted by T. Young (1802) that, in the nineteenth century, led to the replacement of Newton s particle theory of light by a wave theory. 

Some qualities of light are best explained if we describe it as consisting of moving particles, often called photons or quanta (called the particle theory of light). Other qualities are best explained if... 

Perhaps the exception to this is the wave and particle theories of light. 

In order to explain these facts, Einstein therefore proposed a particle theory of light and X-rays. According to this theory... 

The wave particle theory of electrons and protons is analagous to the wave particle theory of light. The distribution of the effects observed can be calculated correctly by a wave theory, but the effects observed are such as might be expected to be produced by particles and not by waves. Neither the waves nor the particles are directly observed. 

Figure 3.4 Sir Isaac Newton (1641-1727), who among many things discovered the laws of universal gravitation and was a proponent of the particle theory of light. (Published with permission from the Deutsches Museum, Munich.)...

Sir Isaac Newton was one of the most frimous scientists to put forward the particle theory of light. Dutch scientist Christiaan Huygens was a contemporary of Newton s who advocated the wave theory of light. This debate between wave theory and particle theory continued into the nineteenth century. Trench physicist Augustinjean Eresnel was influential in the acceptance of the wave theory through his experiments in interference and diffraction. 

In the early twenty-first century it is generally accepted that both the wave and the particle theories are correct in describing optical events. For some optical situations hght behaves as a wave and for others the particle theory is needed to explain the situation. Quantum physics tries to explain the wave-particle duality, and it is possible that future work will unify the wave and particle theories of light. 

The photoelectric effect that supports the particle theory of light was discovered by German physicist Heinrich Rudolph Hertz in 1887 and later by Albert Einstein. When light waves hit a metallic surface electrons are emitted. This effect is used in the generation of solar power. 

Some scientists have commented that the wave and particle theories of light are perhaps a temporary solution to the true understanding of light... 

The Schrodinger equation was first applied to electromagnetic radiation in 1927 by Paul Dirac [26]. The notion of a quantized radiation field that emerged from this work reconciled some of the apparent contradictions between earlier wave and particle theories of light, and as we will see in Chap. 5, led to a consistent explanation of the spontaneous fluorescence of excited molecules. 

---