Question

If the refracted rays from a convex lens are travelling parallel to the principal axis, then image distance is

• A. Equal to object distance
• B. Infinity
• C. Equal to radius of curvature of the lens
• D. Equal to focal length of the lens

Answer 1

The Correct Option is B

To solve the problem, we need to analyze the behavior of refracted rays from a convex lens when they travel parallel to the principal axis.

1. Understanding the Ray Behavior:
In the case of a convex lens, rays of light that are incident parallel to the principal axis converge at the focal point on the opposite side of the lens.
However, in this question, it is stated that the **refracted rays themselves** are travelling parallel to the principal axis.

2. Interpreting the Ray Direction:
If the refracted rays are parallel to the principal axis, then it means the object was placed at the **focus** of the lens.\\ This is because when light rays pass through a convex lens from the focal point, they emerge parallel to the principal axis.

3. Resulting Image Formation:
When refracted rays are parallel, they never meet — not even at infinity — thus no real image is formed.
This implies the rays appear to meet at infinity, and the image is formed at infinity.

Final Answer:
The image distance is $ \text{Infinity} $