lens

• Types of lenses

  • Convex
  • Concave
• Convex lens


  • A lens is a transparent material like glass, with a smooth shape that is either thicker at the edges or thicker in the middle
  • The lens acts like a series of prisms of different angles, which use refraction to point rays in a particular direction
  • The kind of lens which points rays toward a converging point is called a convex lens, aka converging lens
  • The point of convergence of a convex lens is called the principal focus or just the focus, and the distance from the centre of the lens to the focus is called focal length
  • The symbol ↕ is used to represent a convex lens without drawing the whole thing
  • Uses include lamps, telescopes, and binoculars
• Convex lens properties


  • The lens either lets you make a small real image of a far away target, or a large virtual image of a close up target
  • If the image is larger than the real object, the image is said to be magnified
  • Magnification is a ratio of how much larger the image is than the target: e.g. Twice as large, 3.5x as large, 400% larger, 10x, etc.
• Concave lens


  • The concave lens is thinner in the middle and its lens type symbol points the arrows inward like a cursor
  • A concave aka a diverging lens causes rays to diverge away from each other
  • Although the lens is considered to have a focus, the real light rays can never converge at the focus
  • Uses include lasers, and glasses which correct near-sightedness
• Properties of the two types of lenses

  • Convex Lens
  • Concave lens
• Convex lens


  Also known as converging lens
• Concave lens


  Also known as diverging lens
• Convex lens can possibly produce a real image if the target is far away
• Concave lens never produces a real image
• If a real image is produced by a convex lens, it can be projected onto a screen
• Concave lens corrects near-sightedness