When a photon collides with an electron, the interaction is not simply a matter of wavelength change. Photons are elementary particles without rest mass, and their behavior is described by quantum mechanics. Electrons, on the other hand, are massive particles with both particle and wave-like properties.
In a collision between a photon and an electron, several outcomes are possible:
Elastic scattering: The photon interacts with the electron, but both particles emerge from the collision with their original energies and momenta. In this case, there is no change in the photon's wavelength.
Inelastic scattering: The photon transfers some of its energy to the electron, causing it to undergo a transition to a higher energy level within an atom or molecule. The photon's energy decreases, and consequently, its wavelength may change. However, it's important to note that the interaction is more complex than a simple wavelength change.
Absorption: The electron absorbs the entire energy of the photon, transitioning to a higher energy state or being completely ejected from an atom. In this case, the photon ceases to exist, and it's not appropriate to speak of its wavelength afterward.
In any case, the change in momentum resulting from the interaction between a photon and an electron cannot be determined solely by subtracting the initial and final wavelengths and applying the De Broglie's equation. The behavior of particles at the quantum level requires a more comprehensive approach, considering conservation laws, wave-particle duality, and the specific details of the interaction.