Energy from a laser beam

  • Thread starter sgoeke
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Homework Statement


Determine the amount of energy carried in 1 m of a 3.5 mW He-Ne laser beam if the cross-sectional area of the beam is 5x10^-6 m^2.


Homework Equations


J/s = Watt


The Attempt at a Solution


I converted the mW to W. I feel like I should put .0035W over 5x10^-6 m^2 to get intensity. But I don't know where intensity comes into this problem or where the other 1 m comes in.
 

Answers and Replies

  • #2
berkeman
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Homework Statement


Determine the amount of energy carried in 1 m of a 3.5 mW He-Ne laser beam if the cross-sectional area of the beam is 5x10^-6 m^2.


Homework Equations


J/s = Watt


The Attempt at a Solution


I converted the mW to W. I feel like I should put .0035W over 5x10^-6 m^2 to get intensity. But I don't know where intensity comes into this problem or where the other 1 m comes in.

What is energy in terms of power and time? How long does it take light to travel 1 meter?

And remember that sometimes in problems, you may not need everything that you are given...
 

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