Question

How was the idea of light quanta received by other physicists?

Answer 1

At the start of the twentieth century, scientists believed that they understood the most fundamental principles of nature. Atoms were solid building blocks of nature; people trusted Newtonian laws of motion; most of the problems of physics seemed to be solved. However, starting with Einstein's theory of relativity which replaced Newtonian mechanics, scientists gradually realized that their knowledge was far from complete. Of particular interest was the growing field of quantum mechanics, which completely altered the fundamental precepts of physics.

Quantum theory tells us that both light and matter consists of tiny particles which have wavelike properties associated with them. Light is composed of particles called photons, and matter is composed of particles called electrons, protons, neutrons. It's only when the mass of a particle gets small enough that its wavelike properties show up.

To help understand all this let's look at how light behaves as a wave and as a particle.

Wave-like Behavior of Light

In the 1600s Christiaan Huygens, a Dutch physicist, showed that light behaves like a wave.

One behavior of waves is Diffraction

As the width of the slit becomes larger than the wavelength the wave is diffracted less.

Another behavior of waves is Interference

It was James Clerk Maxwell who showed in the 1800s that light is an electromagnetic wave that travels through space at the speed of light. The frequency of light is related to its wavelength according to