Duality (Dual Nature) is a universal character of our life in this Universe. There is an analogy of dual nature of radiation and matter in the domain of Indian Philosophy and Sikh religion, where Ultimate Reality is revealed to exist in its dual nature as sarguna and nirguna Brahman. The concept of Dual Nature of radiation has been in existence since the historical times but it was Max Planck who introduced it on firm footing to explain black body radiation spectrum. Louis de Broglie proposed the concept of dual nature of matter in 1924 in his doctoral thesis. It was established during investigations of Photoelectric effect and Compton effect. The real break-through in interpreting dual nature of matter and radiation may be ascribed to the advent of Quantum Mechanics. It was observed that in the microscopic world of particles, classical concepts of wave and particle fail to justify the experimental investigations; hence there is a need to invoke quantum concepts.
The paper begins with a brief account of classical theory of radiation and its failure to explain black body radiation.It is followed by the introduction of Quantum Theory of radiation by Max Planck.The dual nature of matter by de Broglie has been extensively dealt with.The uncertainty principle of Heisenberg has been critically discussed by many eminent authors who finally concluded it as one of the unavoidable mysteries of nature.As a picture speaks thousand words and as face is the index of the mind, the author has added pictures of eminent physicists at appropriate places.The subject matter of the paper will form a good text for any graduate students of Physics.