What is the average intensity at a distance?

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SUMMARY

The average intensity of a 60 W bulb at a distance of 0.40 m can be calculated using the formula I = P/A, where P is the power and A is the area. Since the bulb radiates light uniformly, the area A is the surface area of a sphere with a radius of 0.40 m, calculated as A = 4πr². Substituting the values, the average intensity is determined to be approximately 118.4 W/m².

PREREQUISITES
  • Understanding of the formula for intensity (I = P/A)
  • Knowledge of surface area calculations for a sphere
  • Familiarity with the concept of power in watts
  • Basic principles of light propagation
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  • Research the calculation of intensity for different power sources
  • Learn about the effects of distance on light intensity
  • Explore the concept of luminous flux and its relation to intensity
  • Study the principles of spherical radiation and its applications
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Students in physics, educators teaching light and optics, and anyone interested in understanding the principles of light intensity and radiation.

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Homework Statement


A 60 W bulb radiates light uniformly in all directions. What is the average intensity of the light bulb at a distance 0.40 m.

Homework Equations


I = P/A, part of my problem is that I don't know the relevant equations

The Attempt at a Solution

 
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Your equation is correct.
You have to assume that the bulb radiates uniformly in all directions, then the area ##A## over which the power is distributed is the surface of a sphere with radius the distance you have.
 
Thank you, that makes so much sense. I thought the area had to be of the object radiating the light.
 

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