How lenses work

• How do lenses focus and disperse light?

  Using refraction
• What are the two main types of lenses?

  Convex and concave lenses
• What shape do convex lenses have?

  Outwards bulge in the center
• What do convex lenses do to parallel rays of light?

  Refract them inwards to a single point
• What is another name for a convex lens?

  Converging lens
• How do concave lenses affect parallel rays of light?

  They refract them outwards
• How do we determine the direction of refracted rays in lenses?

  By tracing virtual lines from the principal focus
• What is the principal focus of a lens?

  The point where light rays converge
• What is another term for the principal focus?

  Focal point
• How many principal foci does a lens have?

  Two, one on each side
• What happens when the direction of light through a lens is reversed?

  Everything flips and focuses on the opposite side
• What is the axis of a lens?

  The line passing through the middle of the lens
• What is the focal length of a lens?

  The distance between the principal focus and the center
• How does the focal length relate to lens power?

  Shorter focal length means more powerful lens
• How can we make a lens more powerful?

  By making it more curved or using stronger materials
• What defines a real image?

  Formed when light rays actually converge
• How is a real image formed in real life?

  Light rays pass through the lens in your eye
• What happens to a real image in terms of orientation?

  It is inverted
• What is a virtual image?

  Formed when light rays do not converge
• What is a common example of a virtual image?

  Image seen in a mirror
• Why can't real rays be behind a mirror?

  Because the mirror is a solid object
• What should you mention when describing images in exams?

  Whether they are real or virtual, upright or inverted
• How would you describe the image on the left in the example?

  Real, inverted, and smaller than the object
• How would you describe the image on the right in the example?

  Virtual, upright, and smaller than the object
• What are the key differences between real and virtual images?

  • Real images:
  • Formed by actual convergence of light rays
  • Can be captured on a screen
  • Typically inverted
  • Virtual images:
  • Formed by traced virtual rays
  • Cannot be captured on a screen
  • Typically upright
• What factors affect the power of a lens?

  • Focal length: Shorter focal length = more power
  • Curvature: More curvature = more power
  • Material: Stronger refractive materials = more power