Focal point

Definition

The focal point is the specific point where light rays parallel to the principal axis converge after passing through a lens or reflecting off a mirror. It is crucial for understanding image formation in optical systems.

5 Must Know Facts For Your Next Test

1. The distance from the lens to the focal point is called the focal length.
2. A convex lens has a positive focal length and converges light rays, forming a real image at its focal point.
3. A concave lens has a negative focal length and diverges light rays, such that they appear to originate from its focal point, forming a virtual image.
4. For mirrors, the type of mirror (concave or convex) determines whether the focal point is real or virtual.
5. In geometric optics, the focal point is essential for determining image location, size, orientation, and type using ray diagrams.

Review Questions

Related terms

Focal Length:

The distance between the center of a lens or mirror and its focal point.

Principal Axis:

An imaginary line that passes through the center of curvature and optical center of a lens or mirror.

Real Image:

An image formed when light rays actually converge at one location. Real images can be projected on a screen.