A concave lens having a material of refractive index `mu_(1)` is kept in a medium of R.I. `mu_(2)`, where `mu_(1) lt mu_(2)`. A parallel beam of light is incident on the lens. The concave lens will act as

Options

A. a diverging lens
B. a converging lens
C. a plane glass slab
D. a plano concave lens

Explanation

To solve the problem, we need to analyze the behavior of a concave lens when it is placed in a medium with a higher refractive index than that of the lens material. Here’s a step-by-step solution:

### Step 1: Understand the Properties of the Concave Lens
A concave lens is a diverging lens that typically causes parallel rays of light to diverge. The lens has a negative focal length, and it is thinner at the center than at the edges.

### Step 2: Identify the Refractive Indices
We are given that:
- The refractive index of the lens material is \( \mu_1 \).
- The refractive index of the medium surrounding the lens is \( \mu_2 \).
- It is stated that \( \mu_1 < \mu_2 \), meaning the lens is in a denser medium.

### Step 3: Analyze the Incident Light
A parallel beam of light is incident on the concave lens. In typical scenarios, when light travels from a medium of lower refractive index to a medium of higher refractive index, it bends towards the normal.

### Step 4: Apply Snell's Law
Using Snell's Law, we can analyze how the light rays behave at the interface of the lens and the surrounding medium. Since \( \mu_2 > \mu_1 \), the light rays will bend towards the normal when entering the lens.

### Step 5: Determine the Effect of the Lens
In this scenario, because the light rays are bending towards the normal upon entering the lens, the concave lens will not behave as it typically does in air (or a less dense medium). Instead, the rays will converge rather than diverge.

### Conclusion
Thus, in this specific case where the concave lens is placed in a medium of higher refractive index, the concave lens will act as a converging lens.

### Final Answer
The concave lens will act as a converging lens when placed in a medium with a higher refractive index.

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