Two thin lenses are placed 5cm apart along the same axis and illuminted with a beam of light parallel to that axis. The first lens in the path of the beam is a converging lens of focal length 10cm whereas the second is a diverging lens of focal length 5cm. If the second lens if now moved toward the first, the emergent light

Options

A. remains parallel
B. remains convergent
C. remains divergent
D. changes form parallel to divergent

Explanation

To solve the problem step by step, we will analyze the situation involving two lenses: a converging lens and a diverging lens, and how the emergent light changes when the diverging lens is moved closer to the converging lens.

### Step 1: Understand the Lens System
We have two lenses:
- **Lens 1**: Converging lens with a focal length (f1) of 10 cm.
- **Lens 2**: Diverging lens with a focal length (f2) of -5 cm (negative because it is a diverging lens).

The distance between the two lenses is given as 5 cm.

### Step 2: Analyze the Initial Condition
When parallel rays of light (from a distant source) strike the converging lens (Lens 1), they converge to a point at its focal length, which is 10 cm from Lens 1.

**Position of the Image Formed by Lens 1**:
- The rays converge at a point 10 cm from Lens 1, which is 5 cm away from Lens 2 (since the distance between the lenses is 5 cm).
- Therefore, the image formed by Lens 1 acts as an object for Lens 2 and is located at a distance of 5 cm from Lens 2.

### Step 3: Determine the Nature of the Rays After Lens 1
Since the image formed by Lens 1 is at the focal point of Lens 2 (which is 5 cm), the rays emerging from Lens 2 will be parallel to each other. This is because when the object is at the focal point of a diverging lens, the emergent rays are parallel.

### Step 4: Moving the Diverging Lens
Now, if we move Lens 2 (the diverging lens) closer to Lens 1, the distance between the two lenses becomes less than 5 cm.

### Step 5: Analyze the New Condition
As Lens 2 moves closer to Lens 1, the image formed by Lens 1 will still be the same, but now the object distance for Lens 2 becomes less than its focal length.

**New Object Distance for Lens 2**:
- The object distance for Lens 2 is now less than 5 cm (the distance between the lenses is reduced).

### Step 6: Determine the Nature of the Rays After Lens 2
When the object distance for Lens 2 is less than its focal length (5 cm), the rays that enter Lens 2 will diverge after passing through it. Thus, the emergent rays from Lens 2 will be divergent.

### Conclusion
Initially, the emergent rays from the system were parallel. After moving the diverging lens closer to the converging lens, the emergent rays become divergent.

### Final Answer
The emergent light changes from parallel to divergent.

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