Lenses

• How does a lens form an image?

  By refracting light
• What are the 2 types of lens?

  Convex and Concave
• Describe the properties of a convex lens?

  A convex lens is wider in the middle than at the edges
• What happens when parallel rays of light enter a convex lens?

  They are brought to a focus at the principal focus (or focal point)
• Why are convex lens sometimes called converging lenses?

  Because the parallel rays of light that enter them come together
• What is the focal length ?

  The distance from the lens to the principal focus
• What happens when parallel rays of light enter a concave lens?

  They spread out , which makes the rays appear to have come from the principle focus on the the same side of the lens that they originated
• Why are concave lens sometimes called diverging lenses?

  Because the parallel rays of light that enter them split
• Convex lenses can produce real or virtual images . Concave lenses can only produce virtual images
• What is a real image?

  It is on the opposite side of the lens to the object and can be projected onto a screen
• What is a virtual image?

  It is on the same side as the object and can only be looked at through the lens