 Good day to all. Welcome to another session. Today's topic is about interaction of x-rays with matter. It is the continuation of the previous session that I have taken as parts of an x-ray machine. So there are four kinds of interactions that are occurring of the x-rays at that of the human body. So first and foremost, some of the primary photons just passes across the human body and reaches the sensor without any interaction. This comprises around 9%. Then followed by the next three interactions, that is the coherent scattering, then the photoelectric effect and the quantum scattering. So in the coherent scattering, the other synonyms given for coherent scattering is Thomson scattering, Rayleigh scattering, classical or elastic scattering. What occurs here is that low energy incident photon interacts with the whole atom. And what happens in here, the incident photon then causes a metrally excitement and then this incident photon ceases to exist. And then this excited atom, it quickly returns to the ground state and generates another x-ray photon which has been deflected or it is formed to be in a different path of that of the incident photon. So this is the scattered photon that is seen here. So that is the net effect is that the direction of the incident x-ray photon has been altered or it has been scattered. So that is why it is called as a coherent scattering. And this comprises around 7%. Moving on to the photoelectric absorption, the incident photon, it tries to interact with the innermost orbital electron. So what happens here is that this electron gets a recoil and this gets that this recoil electron is called as a photoelectron. And what happens here is the void is being created within this innermost shell. So the electron from the next outermost shell that is in from this L shell, it jumps into this and occupies this void. And once this kind of electron that is being occupied into this void, it tries to emit a radiation called as a characteristic radiation. So about 27% of the interactions in a dental x-ray beam exposure, it involves the photoelectric absorption. Next is the pumpkin scattering. In the pumpkin scattering, it comprises about 57% of the interactions in the dental x-ray beam exposure. And what happens here is that the in the flow energy incident photon tries to interact with the outermost shell electron or the outermost orbital electron. It recoils the electron from its orbit and this is how the recoil electron gets emitted. And then what happens is that the incident photon, it ceases to exist and gets deflected in a different path compared to that of the incident photon. So the net effect is that the that is the energy of the scattered photon is found to be equal to that of the energy of the incident photon minus the sum of the kinetic energy that has been gained by this recoil electron and its binding energy. So the content scattering, it comprises around a 57% of interactions in the dental x-ray beam exposure. So to summarize, we spoke about the interactions of how the x-ray photon, it reacts with the human body and then how it reaches in the sensor. So here we have four types that is there is no interaction occurring such that the primary photosys passes across the human body and reaches the sensor with no interaction comprising around 9% followed by the coherent scattering wherein we spoke about it comprises around 7% of the total interactions of the dental x-ray beam exposure then followed by the photo entry absorption and then the content scattering which comprises around the major part of the x-ray beam exposure interaction that is around 57%. Thank you.