What is Compton effect? How is the existence of modified and un modified components explain by Quantum theory?

The Compton Effect is a phenomenon in physics that demonstrates the particle-like properties of light. It was discovered by American physicist Arthur H. Compton in 1923. The Compton Effect refers to the change in direction and decrease in energy (increase in wavelength) of an X-ray or gamma ray photon when it collides with a particle. In this collision, the photon loses energy which is transferred to the particle, causing the photon's wavelength to increase and its direction to change.

The Compton Effect can be explained by quantum theory, which describes light as particles called photons. According to quantum theory, the energy and momentum of photons are related to their frequency (or inversely, their wavelength) and direction of propagation, respectively.

In the Compton Effect, the incident photon gives part of its energy to the electron, and the scattered photon has less energy (or equivalently, a longer wavelength). This is the "modified" component of the scattered light. The "unmodified" component refers to the part of the scattered light that has not interacted with the electrons and therefore has not changed in wavelength.

Quantum theory explains this by the conservation of energy and momentum. The total energy and total momentum before the collision (of the incident photon and the electron) must equal the total energy and total momentum after the collision (of the scattered photon and the recoiling electron). This leads to two equations, which can be solved to find the change in wavelength of the scattered photon. This change in wavelength is directly observed in the Compton Effect, confirming the quantum theory explanation.