The Relationship Between Sound & Light

Think Kilometers

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Think Kilometers

There is also a rule about lightning and thunder that works for kilometers rather than miles: The distance of lightning in kilometers is the time between the appearance of the lightning and the sound of the thunder in seconds, divided by 3.

Think about this rule and consider the following question:

  • If there are 7 sec between the lightning and the sound of thunder, how far away is the lightning in kilometers?
  • Follow the problem-solving process:
    • Understand the situation.
    • Represent the situation.
    • Answer questions about the situation.
    • Check that your answer makes sense.

VIDEO: Lightning and Thunder


  • Use the problem-solving process to help guide your thinking.
  • What is the independent variable in the problem situation? What is the dependent variable? How can you represent these variables on your graph?
  • How can you use a ratio table to help you make your graph?
  • What intervals and scale will you use for your graph?
  • Include the units for all quantities—in calculations, graphs, tables, and so on—to help you make sense of the values.