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Light: Mirrors and Lenses

Behind the glass

Stand in front of a flat mirror. An image is the picture that a mirror or lens shows. Your image seems to stand behind the glass.

An object stands in front of the mirror.
Step 1 of 4
  1. An object stands in front of the mirror.
  2. Two rays travel from it to the mirror.
  3. Both rays leave by the law of reflection.
  4. Followed backward, they cross behind the glass.

The rule

A flat mirror is a plane mirror. Lateral inversion means left and right swap. Upright means not upside down.

The image stands as far behind as the object stands in front. It is the same size and upright. Left and right are swapped.

Example: a pencil stands 3 cm from the mirror. Its image is 3 cm behind the mirror. So the pencil and its image are 3 + 3 = 6 cm apart.

Slide the object. Watch the letter and its image.

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This track

  1. 0 Start here
  2. 1 The law of reflection
  3. 2 Behind the glass
  4. 3 Two more kinds of mirror
  5. 4 Curved mirrors and parallel rays
  6. 5 Light bends
  7. 6 The pencil that looks bent
  8. 7 Lenses
  9. 8 What a lens shows
  10. 9 The big picture
  11. 10 Track quiz

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