When a photon bounce off an electron, it gives some of its energy to the electron. The photon has no mass, however, and it must continue to travel at speed c. How is its reduced energy manifested?
A 5kg fish swimming at 1 m/s swallows an absent minded 1-kg fish swimming toward it at a velocity that brings both fish to a halt. Find the speed of the smaller fish before lunch.
Since the post-lunch momentum is zero, the momentum of larger fish should be equal to the momentum of smaller fish in terms of magnitude but opposite in direction.
Speed of the smaller fish v2:
v2 = (m1*v1)/m2
= 5*1/1 = 5m/s
The photon loses momentum by reducing its frequency. the process is called Compton scattering.
When a photon interacts with an electron and transfers some of its energy to the electron, the reduced energy of the photon is manifested in a reduction of its frequency or wavelength. This change in frequency or wavelength corresponds to a change in the color (or energy) of the photon.
To understand this phenomenon, we need to consider the concept of a photon's energy being proportional to its frequency (E = hf) or inversely proportional to its wavelength (E = hc/λ), where E is the energy, h is Planck's constant, f is the frequency, c is the speed of light, and λ is the wavelength.
When a photon interacts with an electron, it transfers a portion of its energy to the electron, causing the photon's energy to decrease. Since the speed of light (c) remains constant, the reduced energy of the photon must be manifested in a decrease in frequency (f) or an increase in the wavelength (λ).
This change in frequency or wavelength is related to the change in color of the photon. For example, if a high-energy blue photon transfers some of its energy to an electron, it may now have a lower energy that corresponds to a longer wavelength, resulting in a change to a lower energy color, such as red.
It's important to note that even though the energy of a photon can change when it interacts with an electron, its speed (c) remains constant because photons always travel at the speed of light. The change in energy is solely manifested in the photon's frequency or wavelength.