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Candelas and distance

  • #1

Homework Statement


A 10-cd point source lamp and a 70-cd point source lamp cast equal intensities on a wall. If the 10-cd lamp is 8.0 m from the wall, how far from the wall is the 70-cd lamp?



Homework Equations


I'm not sure what the equation for a candela is.


The Attempt at a Solution


Can't attempt it without knowing an equation.


That's the only information given, and I don't know how to form an equation.
 

Answers and Replies

  • #2
674
2
A candela is a unit of intensity for light. And you remember that intensity falls off as 1/r^2.
 

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