Refraction And Lenses Practice Test

In ray tracing for a thin lens, which ray goes through the optical center without bending?

A ray parallel to the axis A ray that passes through the focal point on the object side A ray that passes through the focal point on the image side The ray that goes through the optical center

Correct Answer:

The ray that goes through the optical center

Explanation:

In thin-lens ray tracing, a key rule is that a ray passing through the optical center goes straight without bending. This happens because, in the thin-lens approximation, the two refracting surfaces are so close together that the refractions cancel, so the ray continues along its original path. This undeviated central ray serves as one of the foundational rays used to locate the image, along with the other two standard rays: a ray parallel to the principal axis that refracts through the focal point on the image side, and a ray that passes through the focal point on the object side that exits the lens parallel to the principal axis. By tracing these rays, you can determine where they intersect to find the image position.

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