A long cylindrical tube containing water in closed by an equinvex lens of focal length 10 cm in air. A point source is placed along the axis of the tube outside it at a distance of 21 cm from the lens. Locate the final image of the source. Refractive index of the materials of the lens `=1.5 ` and that of water `=1.33.`

Explanation

To solve the problem, we will follow these steps:

### Step 1: Identify the parameters
- Focal length of the lens in air, \( f = 10 \, \text{cm} \)
- Object distance from the lens, \( u = -21 \, \text{cm} \) (negative as per sign convention)
- Refractive index of the lens, \( \mu_{\text{lens}} = 1.5 \)
- Refractive index of water, \( \mu_{\text{water}} = 1.33 \)

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