Planck's Quantum Theory changed the view of Physicists

Introduction

By the late 18th century there was a great progress in the field of Physics. However by the early 20th century many phenomena could not be predicted by Classical (Newtonian) Physics which was widely accepted at that time. Classical Mechanics failed especially at the atomic levels and completely contradicted with the modern experiments like photoelectric effect. As a result a new set of theories were articulated and these was collectively called Quantum Mechanics. Quantum mechanics changed the view of how Physicists viewed the Universe. It marked the end of a Clockwise Universe (Idea that a universe is predictable).

EM Waves

Electromagnetic (EM) radiation is a form of energy with both wave and particle nature; visible light being a well-known example. From the wave perspective, all forms of EM radiation may be described in terms of their wavelength and frequency. While the wavelength and frequency of EM radiation may vary, its speed in a vacuum remains constant at c=3.0 x 10⁸ m/sec, the speed of light. The wavelength or frequency of any specific occurrence of EM radiation determine its position on the electromagnetic spectrum and can be calculated from the following equation:

                                                          c=νλ
where λ = wavelength in meters, and ν=frequency in hertz (1/sec).

Discovery of Quantum (Photoelectric Effect)

Photoelectric effect is observed when light focused on certain metals emits electrons.This effect occurs when an EM radiation greater than a certain frequency falls on a metal. This minimum threshold frequency also called cutoff frequency is different for different metals. One important observation was that the emission of electrons did not depend on intensity of incident light, i.e. even light with twice intensity and a frequency less than the the threshold was unable to emit electrons. This was contrary to the effect that was expected if the light acted as a wave strictly; the effect of light would then be cumulative adding up the intensities little by little until electrons are emitted. But instead there is a clear cutoff frequency which triggers this phenomena known as photoelectric emission. This led to the conclusion that the energy of light is directly proportional to the frequency, higher light frequencies have greater energy. This led to the discovery that an atom could loss or gain a minimum amount of energy this minimum energy being called "quantum" plural "quanta". One photon of light carries one quantum of energy. According to Planck we have
                                                           E=hν

                         where h is Planck's constant and h=6.634x10^-34