Lenses

• 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 differ from convex lenses?

  They cave in on either side
• What do concave lenses do to parallel rays of light?

  Refract them outwards to disperse
• How do we determine the direction of refracted rays?

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

  The point where light rays converge
• What is the relationship between the principal focus and the lens's center?

  They are equal distances apart
• What is another term for the principal focus?

  Focal point
• What happens when the direction of light is reversed through a lens?

  Everything flips and focuses on the opposite side
• Where does the principal focus always sit?

  On the axis of the lens
• What is the distance between the principal focus and the lens's center called?

  Focal length
• How does the focal length relate to the power of a lens?

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

  By making it more curved or using stronger material
• What is the difference between real and virtual images?

  Real images are formed by actual light convergence
• How is a real image formed?

  When light rays actually converge to form the image
• What happens to light rays from an object like a spanner?

  They form a real image on the retina
• Why don't we notice the inversion of real images?

  Our brain corrects the inverted image
• How are virtual images formed?

  When light rays do not actually converge
• 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