GCSE Physics Tutorial - Define Activity
In this tutorial, we will explore the concept of activity in the context of nuclear physics. Activity is a fundamental measure used to quantify the rate at which a radioactive substance undergoes decay. It provides crucial information about the intensity of radiation emitted by a radioactive source. Let's delve into the definition and key aspects of activity.
Definition of Activity: Activity, denoted by the symbol "A," is a measure of the rate of radioactive decay of a substance. It represents the number of radioactive decays that occur per unit of time within a given radioactive source.
Units of Activity: The standard unit of activity in the International System of Units (SI) is the Becquerel (Bq). One Becquerel is equal to one radioactive decay per second (1 Bq = 1 decay/s).
Curie and Rutherford: In older non-SI units, the Curie (Ci) and the Rutherford (rd) were used to express activity: a. Curie (Ci): One Curie represents 3.7 x 10^10 decays per second (1 Ci = 3.7 x 10^10 Bq). b. Rutherford (rd): One Rutherford represents 10^6 decays per second (1 rd = 10^6 Bq).
Activity and Half-Life: The activity of a radioactive substance is directly related to its half-life. As the half-life decreases, the activity increases because more radioactive decays occur in a given time period.
Measuring Activity: Activity can be measured using a radiation detector, such as a Geiger-Muller counter or a scintillation detector. These instruments detect and count the radioactive decays emitted by a radioactive source.
Decay Constant: The rate of radioactive decay is governed by the decay constant (λ). The decay constant represents the probability of a single radioactive decay occurring in a given unit of time. It is related to the half-life (T½) by the equation: λ = ln(2) / T½.
Calculating Activity: The activity (A) of a radioactive substance can be calculated using the formula: A = λ * N, where N is the number of radioactive nuclei present in the sample.
Importance of Activity: Activity is a crucial parameter in understanding and managing radioactive materials. It is used in various applications, including nuclear medicine, radiography, and industrial applications.
In this tutorial, we have defined activity as the rate of radioactive decay of a substance. It is a measure of the number of radioactive decays that occur per unit of time within a radioactive source. Activity is quantified using the SI unit Becquerel (Bq) and provides essential information about the intensity of radiation emitted by a radioactive material. The activity of a substance is directly related to its half-life and decay constant. Understanding activity is fundamental in nuclear physics and plays a vital role in various practical applications, such as nuclear medicine and industrial uses of radioactive materials.
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