Which type of radiation is involved in the photoelectric effect?

• A. X-rays
• B. Ultrasound
• C. Gamma rays
• D. Infrared radiation

Answer: (A)

The photoelectric effect involves the interaction of photons with matter, resulting in the ejection of electrons from atoms. X-rays are a form of electromagnetic radiation with sufficient energy to cause this effect. When X-ray photons strike a material, particularly dense tissues like bone, they can transfer their energy to electrons in the atoms of that material. If the energy of the X-ray photon exceeds the binding energy of the electron in the atom, the electron is ejected, contributing to the overall radiation interaction.

Other types of radiation, such as ultrasound, gamma rays, and infrared radiation, operate under different principles or energies. Ultrasound utilizes sound waves rather than electromagnetic radiation and does not involve the photoelectric effect. Gamma rays, while still capable of causing electron ejection, typically interact with matter through other mechanisms such as Compton scattering or pair production at significantly high energies. Infrared radiation has lower energy than X-rays and is typically associated with vibrational transitions rather than ionization or the ejection of electrons. Thus, X-rays are distinct in their capability to directly cause the photoelectric effect due to their ionizing nature.