A polychromatic beam of X-Rays has an energy spectrum as shown in Figure P below. Which of the following graphs (in the options A to D) depicts the energy spectrum after passing through a human body? In each figure, the horizontal axis represents Energy in keV and the vertical axis represents Relative X-ray Intensity.
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- X-rays after passing through matter show \textbf{beam hardening}: low-energy photons get absorbed more.
- The output spectrum shifts towards higher energies with reduced intensity overall.
- Characteristic peaks remain but with lower amplitudes.
Step 1: When X-rays pass through a human body, lower energy photons are absorbed more strongly than higher energy photons due to the photoelectric effect. This process is called beam hardening. Step 2: As a result, the transmitted spectrum after passing through the body will have reduced intensity at lower energies while the higher energy components are less attenuated. Step 3: The characteristic peaks remain in the spectrum since they correspond to the target material (e.g., tungsten) and pass through with reduced but noticeable intensity. Step 4: Among the given options, graph (A) best depicts this effect: it shows a decrease in intensity overall, with the low-energy side suppressed more strongly while the high-energy side remains relatively stronger.
