The electron is in rest initially.squareroot said:
Through experiments and observations, scientists have found that when a photon is absorbed by a free electron, the electron can only gain a certain amount of energy. This indicates that the electron did not fully absorb the photon.
One key piece of evidence is the conservation of energy. If a free electron were able to fully absorb a photon, it would gain an infinite amount of energy, which is not possible according to the laws of thermodynamics. Additionally, experiments have shown that the energy gained by an electron upon absorbing a photon is always less than the energy of the photon itself.
Electrons have discrete energy levels, meaning they can only exist at specific energy levels and cannot have any amount of energy in between. When a photon is absorbed, it can only transfer a specific amount of energy to the electron that corresponds to one of these energy levels. This prevents the electron from fully absorbing the photon.
No, there is no known circumstance in which a free electron can fully absorb a photon. However, in certain materials with specific energy band structures, electrons can absorb photons and jump to higher energy levels, giving the appearance of full absorption. But in reality, the electron is still not fully absorbing the photon.
The photoelectric effect, in which electrons are ejected from a material when it is exposed to light, is a phenomenon that cannot be fully explained by classical physics. The concept that a free electron cannot fully absorb a photon helps to explain why only certain frequencies of light can cause the ejection of electrons and why there is a threshold frequency. This has led to the development of quantum mechanics, which provides a more complete understanding of the photoelectric effect.