The unit of radioactivity decay rate is

Options

A. Curie
B. Becquerel
C. decay per second
D. all of these

Answer

To determine the unit of radioactivity decay rate, we can follow these steps:

### Step 1: Understand the Concept of Decay Rate
Radioactivity decay rate refers to the number of disintegrations or decays that occur in a radioactive sample over a specific period of time. This is a measure of how quickly a radioactive substance is decaying.

**Hint:** Remember that decay rate is related to how many atoms are disintegrating per unit time.

### Step 2: Define the Mathematical Expression
The decay rate can be mathematically expressed as:
\[ \text{Decay Rate} = -\frac{dN}{dt} \]
where \(dN\) is the change in the number of radioactive nuclei and \(dt\) is the change in time.

**Hint:** Look for the relationship between the change in quantity and time to understand the decay rate.

### Step 3: Identify the SI Unit
The SI unit of radioactivity is defined as the number of disintegrations per second. This unit is known as the **Becquerel (Bq)**.

**Hint:** Recall that SI units are standardized units used in scientific measurements.

### Step 4: Understand Other Units
While the Becquerel is the standard SI unit, there are other units such as the **Curie (Ci)**. One Curie is equivalent to \(3.7 \times 10^{10}\) disintegrations per second, which is also equal to \(3.7 \times 10^{10}\) Becquerels.

**Hint:** Be aware of historical units and their conversions to SI units.

### Step 5: Conclusion
Thus, the unit of radioactivity decay rate is:
- **Becquerel (Bq)** or
- **Disintegrations per second (dps)**.

Both terms refer to the same measurement of decay rate.

**Final Answer:** The unit of radioactivity decay rate is **Becquerel (Bq)**, which is equivalent to disintegrations per second.