A student measures the thickness of a human hair using a microscope of magnification 100. He makes 20 observations and find that the average thickness (as viewed in the microscope) is 3.5 mm. What is the estimate of the thickness of hair?

Options

A. `0.5cm`
B. `0.035 ` cm
C. `0.035` mm
D. 3.5 cm

Answer

To estimate the thickness of the human hair based on the measurements taken by the student using a microscope, we can follow these steps:

### Step 1: Understand the given information
- The magnification of the microscope is 100.
- The average thickness of the hair as viewed through the microscope is 3.5 mm.

### Step 2: Use the formula for original thickness
The original thickness of the hair can be calculated using the formula:
\[ \text{Original Thickness} = \frac{\text{Measured Thickness}}{\text{Magnification}} \]

### Step 3: Substitute the values into the formula
Substituting the given values into the formula:
\[ \text{Original Thickness} = \frac{3.5 \text{ mm}}{100} \]

### Step 4: Perform the calculation
Now, calculate the original thickness:
\[ \text{Original Thickness} = 0.035 \text{ mm} \]

### Step 5: Convert the thickness to the desired unit (if necessary)
Since the question asks for the estimate of the thickness of hair, we can leave it in millimeters, which gives us:
\[ \text{Thickness of hair} = 0.035 \text{ mm} \]

### Conclusion
Thus, the estimate of the thickness of the hair is **0.035 mm**.

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