Images Formed By Lenses

Key Notes :

Introduction to Lenses:

  • Lenses are transparent curved pieces of glass or plastic that can bend light rays.
  • There are two main types of lenses: convex and concave.

Convex Lenses:

  • Convex lenses are thicker in the middle and thinner at the edges.
  • They are also called converging lenses because they converge (bring together) light rays.
  • Convex lenses can form real or virtual images depending on the object’s position relative to the lens.

Concave Lenses:

  • Concave lenses are thinner in the middle and thicker at the edges.
  • They are also called diverging lenses because they diverge (spread out) light rays.
  • Concave lenses always form virtual images.

Image Formation with Convex Lenses:

  • Convex lenses can form two types of images: real and virtual.
  • Real images are formed when light rays actually converge to a point on the opposite side of the lens.
  • Virtual images are formed when extended light rays appear to converge on the same side as the object.
  • The position and size of the image depend on the object’s distance from the lens.

Image Characteristics:

  • Images can be:
    • Real and inverted (upside down).
    • Real and upright.
    • Virtual and upright.
  • The size of the image can be:
    • Larger than the object.
    • Smaller than the object.
    • The same size as the object.

Lens Equation:

  • The lens equation relates the object distance (do), image distance (di), and focal length (f) of the lens:
    • 1/f = 1/do + 1/di

Focal Length:

  • The focal length is the distance between the lens and the point where parallel rays of light converge (or appear to converge) after passing through the lens.
  • Convex lenses have positive focal lengths, while concave lenses have negative focal lengths.

Examples of Lens Applications:

  • Convex lenses are used in eyeglasses to correct farsightedness or nearsightedness.
  • Cameras and telescopes use convex lenses to form images.
  • Concave lenses are used in glasses to correct double vision (diplopia).

Summary:

  • Lenses are transparent curved objects that can bend light rays.
  • Convex lenses converge light and can form real or virtual images.
  • Concave lenses diverge light and always form virtual images.
  • The type, size, and position of the image depend on the object’s distance from the lens.

Let’s practice!