Radioactivity: Understanding Its Measurement

The question asks about the unit used to measure the intensity of radioactivity. The term "intensity of radioactivity" often refers to the activity of a radioactive source, which describes how many atomic nuclei disintegrate or decay per unit of time.

Radioactivity: What is It?

Radioactivity is a natural process where unstable atomic nuclei spontaneously decay, releasing energy and particles (like alpha particles, beta particles, or gamma rays). This process transforms the unstable nucleus into a more stable one. The rate at which these disintegrations occur is what we measure as the activity or "intensity" of the radioactive source.

Units for Measuring Radioactivity Intensity

There are primary units used to quantify the intensity of radioactivity:

• Curie (Ci): This is a traditional, non-SI unit of radioactivity. It was originally defined based on the activity of one gram of radium. One Curie is defined as the activity corresponding to \(3.7 \times 10^{10}\) nuclear disintegrations per second. It's a very large unit, often used for sources with significant activity.
• Becquerel (Bq): This is the SI (International System of Units) unit of radioactivity. One Becquerel is defined as one nuclear disintegration per second. Therefore, \(1 \text{ Bq} = 1 \text{ disintegration/second}\). The relationship between Curie and Becquerel is: \[ 1 \text{ Curie (Ci)} = 3.7 \times 10^{10} \text{ Becquerels (Bq)} \]

Analyzing the Options

Let's look at the given options in the context of measuring radioactivity intensity:

• Decibel (dB): Decibel is a logarithmic unit used to express the ratio of two values of a physical quantity, such as power or sound intensity. It is commonly used in acoustics, electronics, and signal processing. It has no relation to the measurement of radioactivity.
• Curie (Ci): As discussed, Curie is indeed a widely recognized unit for measuring the activity or intensity of radioactivity. It quantifies the number of radioactive decays occurring per second.
• Hertz (Hz): Hertz is the SI unit of frequency, defined as one cycle per second. While radiation can be described by its frequency (e.g., electromagnetic waves), Hertz does not measure the rate of radioactive decay or the overall intensity of a radioactive source.
• None of these: This option would be correct if none of the above units were suitable. However, Curie is a direct measure of radioactivity intensity.

Based on the analysis, Curie is the correct unit for measuring the intensity of radioactivity, as it directly quantifies the rate of nuclear disintegrations.