Concave Lenses

Definition

• Concave lenses have surfaces that "cave" inward.
• They are symmetric, with both surfaces typically assumed to be concave.

Principal Axis and Focal Points

• Principal axis is a straight line passing through the center of the lens.
• Two focal points are equidistant on either side of the lens.

Ray Diagram for Concave Lenses

• Object Placement: When an object is placed on the left side of a concave lens.
• Ray 1: Travels parallel to the principal axis and diverges outwards, appearing to originate from the focal point on the same side.
• Ray 2: Passes straight through the center of the lens without diffraction.

Image Formation

• Image Type: Virtual image
  • Rays appear to diverge from a point on the side of the object.
  • The virtual image is upright, not inverted.
• Size and Position:
  • The image is smaller than the object.
  • Appears closer to the lens than the actual object.

Important Points

• Concave lenses do not form real images because the refracted rays diverge.
• The virtual image is seen by an observer looking through the lens.

Conclusion

• Concave lenses primarily create smaller, virtual images that are closer to the lens than the object itself.