The hypothesis is suggested that when an X-ray quantum is scattered it spends all of its energy and momentum upon some particular electron. In this paper, we study light diffraction with the relativistic quantum theory approach. — A quantum theory of the scattering of X-rays and p-rays by light elements. If light behave only as a wave, then prism should give a continuous rainbow. This electron in turn scatters the ray in some definite direction. Applications of Planck’s Quantum Theory Planck’s quantum theory is the fundamental theory of quantum mechanics. The classical picture underlying the photoelectric effect was that the atoms in the metal contained electrons, that were shaken and caused to vibrate by the oscillating electric field of the incident radiation. One phenomenon that seemed to contradict the theories of classical physics was blackbody radiation, which is electromagnetic radiation given off by a hot object. Practically it is not possible to construct a perfect black body. Emission spectrum of nitrogen gas also supports Planck’s quantum theory of radiation. However, the effect of slit thickness on the diffraction pattern cannot be explained by wave-optical approach, but it can be explained in quantum theory. While working with a spark-gap transmitter, Hertz discovered that upon absorption of certain frequencies of light, substances would give off a visible spark. PLANCK'S QUANTUM THEORY . color) of radiant energy emitted by a blackbody depends … We find that the slit length, slit width, slit thickness and wavelength of light affect the diffraction intensity and form of diffraction pattern. In the year 1900, in order to explain black body radiations, Max Planck proposed Quantum theory by considering light to possess particle nature. This also supports Planck’s Quantum Theory. Today a more complete description is given by the theory of quantum electrodynamics (QED), which is a part of a more general relativistic quantum ﬁeld theory (the standard model) that describe the physics of the elementary particles. Blackbody Radiation. Black body: The object which absorbs and emits the radiation of energy completely is called a black body. About this time, the atomic theory and the corpuscular theory of light (as updated by Einstein)[1] first came to be widely accepted as scientific fact; these latter theories can be viewed as quantum theories of matter and electromagnetic radiation, respectively. The wavelength (i.e. Einstein's early contributions to quantum theory include his heuristic suggestion that light behaves as if it is composed of photons, and his exploration of the quantum structure of the mechanical energies of particles embedded in matter.