Compared to the incident X-rays, the cascade photons have: A. Lower energy B. Sh

Question

Compared to the incident X-rays, the cascade photons have: A. Lower energy B. Shorter wavelength C. Higher speed Passage I Short wavelength electromagnetic rays called X-rays are often used to image internal anatomical structures. Some parts of the body are nearly transparent to X-rays, while others are relatively opaque. A picture is taken of the shadow cast under X-ray illumination. The intensity of a beam of X-rays transmitted through a medium is given by where I, is the intensity incident on the medium, is the absorption coefficient of the medium (which is dependent upon the density of the medium), and x is the distance traveled through the medium. Like other electromagnetic waves, the frequency/and the wavelength of a beam of X-rays satisfy the relations c=M and E=hf where c is the speed of light in a vacuum, E is the energy of a photon, and h is Plank's constant. (Note: h = 6.62 x 10-34 m 3kg/s, 1 eV = 1.6 x 10-19 Joules.) X-rays interact with atoms primarily via collisions with electrons in low atomic energy levels. The probability of a collision with an electron in a neutral atom is proportional to the fourth power of the nuclear charge. In this type of collision, the electron is frequently ejected from the atom. A higher level electron falls down to fill the vacancy, emitting a long wavelength photon in the process and creating a new vacancy at a higher energy level. This process continues until there are no electrons at higher energy levels to fall to a lower state, leaving a single vacancy. The atom is then singly-ionized. This rapid emission of photons is called a cascade. Geiger counters measure the intensity of X-rays by maintaining a high voltage difference between a wire and the metal wall of a gas chamber. Free electrons created by radiation-induced ionization are accelerated toward the wire so rapidly they ionize even more atoms in the gas. This ionization avalanche causes the counter to click

Explanation / Answer

Compare to incident X-ray photons the Cascade photons will have Lower energy. Beacuse the Cascade photons are being generated by the transition of higher level electron into lower energy state which was vancent due to the ejection of lower level electron and that ejection was due to incident x-ray photon. It is clear that for this process energy of incident x-ray would be greater than ionization energy of the atom while the cascade photons energy is due to transition between two levels of the same atom So it would be lower compare to incident x-ray photon.

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