A concave lens of glass, refractive index 1.5 has both surfaces of same radius of curvature R. On immersion in a medium of refractive index 1.75, it will behave as a

Options

A. convergent lens of focal length 3.5 R
B. convergent lens of focal length 3.0 R
C. divergent lens of focal length 3.5 R
D. divergent lens of focal length 3.0 R

Explanation

To determine how a concave lens of glass (refractive index 1.5) behaves when immersed in a medium with a refractive index of 1.75, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Refractive Indices**:
- Refractive index of the lens, \( \mu_L = 1.5 \)
- Refractive index of the surrounding medium, \( \mu_S = 1.75 \)

2. **Determine the Behavior of the Lens**:
- A lens is considered to be a converging lens (convex) if its refractive index is greater than that of the surrounding medium, and a diverging lens (concave) if its refractive index is less than that of the surrounding medium.

3. **Compare the Refractive Indices**:
- Since \( \mu_L (1.5) < \mu_S (1.75) \), the lens will behave as a diverging lens (concave lens) when immersed in the medium.

4. **Conclusion**:
- Therefore, the concave lens will continue to behave as a concave lens even when immersed in the medium of higher refractive index.

### Final Answer:
The concave lens of glass (refractive index 1.5) will behave as a concave lens when immersed in a medium of refractive index 1.75.

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