According to the accompanying animation, the photoelectric effect accounts for absorbed dose.

According to the accompanying animation, the photoelectric effect accounts for absorbed dose.

• A. Occurs with high energy photons
• B. Involves emission of an outer-shell electron
• C. Occurs in heavy elements
• D. Accounts for absorbed dose

Answer: (D)

The key idea is that absorbed dose comes from energy actually deposited in the tissue when photons are absorbed by matter. In the photoelectric effect, a photon is completely absorbed and ejects an inner-shell electron. The energy of that photon becomes the kinetic energy of the ejected electron (and any energy released during subsequent atomic relaxation), all of which remains in the surrounding tissue and contributes to the absorbed dose. That direct transfer of photon energy to the tissue is exactly what absorbed dose measures, so saying the photoelectric effect accounts for absorbed dose captures the essential relationship. The other statements don’t match the main idea as well: the photoelectric effect tends to occur at lower photon energies rather than high energies; it involves inner-shell electrons, not outer-shell ones; and while it is more likely in heavy elements, that chemical detail doesn’t by itself explain why it contributes to absorbed dose.

The key idea is that absorbed dose comes from energy actually deposited in the tissue when photons are absorbed by matter. In the photoelectric effect, a photon is completely absorbed and ejects an inner-shell electron. The energy of that photon becomes the kinetic energy of the ejected electron (and any energy released during subsequent atomic relaxation), all of which remains in the surrounding tissue and contributes to the absorbed dose. That direct transfer of photon energy to the tissue is exactly what absorbed dose measures, so saying the photoelectric effect accounts for absorbed dose captures the essential relationship.

The other statements don’t match the main idea as well: the photoelectric effect tends to occur at lower photon energies rather than high energies; it involves inner-shell electrons, not outer-shell ones; and while it is more likely in heavy elements, that chemical detail doesn’t by itself explain why it contributes to absorbed dose.