A mercury thermometer is to be made with glass tubing of internal bore 0.5 mm diameter and the distance between the fixed point is to be 20 cm. Estimate the volume of the bulb below the lower fixed point, given that the coefficient of cubical expansion of mercury is `0.00018//K`. and the coefficient of linear expansion of glass is `0.000009//K`.

Explanation

To estimate the volume of the bulb below the lower fixed point of a mercury thermometer, we can follow these steps:

### Step 1: Determine the radius of the glass tubing.
The internal diameter of the glass tubing is given as 0.5 mm. To find the radius (r), we use the formula:
\[ r = \frac{\text{diameter}}{2} = \frac{0.5 \text{ mm}}{2} = 0.25 \text{ mm} = 0.25 \times 10^{-3} \text{ m} \]

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