Final answer:
A scintillation counter uses a scintillator crystal to detect and measure ionizing radiation, whereas a Geiger-Müller counter uses ionization within a gas tube. The correct answer to the student's question is B) Scintillation counter.
Step-by-step explanation:
The instrument that uses a crystal to detect and measure counts of ionizing radiation by means of the light (luminescence) produced when radiation excites a scintillator material is known as a scintillation counter. Unlike a Geiger-Müller counter, which uses the ionization of gas within a tube to detect radiation, the scintillation counter has a scintillator crystal that emits light when struck by radiation; this light is then converted into an electric signal by a sensor, typically a photomultiplier tube. Therefore, the correct answer to the student's question is B) Scintillation counter.
A scintillation counter is the instrument that uses a crystal to detect and measure counts of radiation. It contains a scintillator, a material that emits light when excited by ionizing radiation, and a sensor that converts the light into an electric signal. This instrument is commonly used to measure ionizing radiation and determine personal radiation exposure.