One Dobson unit is equal to a layer of pure ozone ...... in thickness at standard temperature and pressure .

Options

A. 1 mm
B. 0.1 mm
C. 0.01 mm
D. 0.001 mm

Answer

To solve the question regarding the thickness of a layer of pure ozone that corresponds to one Dobson unit at standard temperature and pressure, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Dobson Unit**:
- A Dobson unit (DU) is a measurement used to quantify the amount of ozone in the atmosphere. It indicates the thickness of a layer of ozone that would be present if all the ozone in a column of the atmosphere were brought down to standard temperature and pressure (STP).

2. **Know the Standard Temperature and Pressure**:
- Standard temperature is defined as 0 degrees Celsius (273.15 K) and standard pressure is defined as 1 atmosphere (atm).

3. **Determine the Thickness of Ozone for One Dobson Unit**:
- According to scientific data, one Dobson unit is equivalent to a thickness of 0.01 millimeters (mm) of pure ozone at standard temperature and pressure.

4. **Conclusion**:
- Therefore, the answer to the question is that one Dobson unit is equal to a layer of pure ozone that is 0.01 mm in thickness at standard temperature and pressure.

### Final Answer:
One Dobson unit is equal to a layer of pure ozone **0.01 mm** in thickness at standard temperature and pressure.

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