Focus of a Parabolic Reflector
As the shape of a parabolic reflector changes, the focal point moves. You can discover this effect for yourself by playing with the parabola below.
  • By increasing 'a' you can make the parabola narrower.
  • Press the 'Beam' button to send a beam of waves toward the parabola. (They will reflect through the focus).
  • Pressing the 'Init' button returns the parabola to its original shape.

Try to answer these questions:
  1. As the parabola gets narrower, which way does the focus move?
  2. As the parabola gets wider, which way does the focus move?
  3. If you could widen the parabola to a line, where would the focus be?
  4. Which real objects make use of this phenomenon?
        (Think about sound and light)

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