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A 40-W lightbulb is 2.2 m from a screen. What is the intensity of light incident...

A 40-W lightbulb is 2.2 m from a screen. What is the intensity of light incident on the screen? Assume that a lightbulb emits radiation uniformly in all directions (i.e., over 4π steradians).

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Answer #1

formula for intensity

I = P/A

since lightbulb emits radiation uniformly in all directions

A= 4 pi r^2

I = P/ 4pi r^2

=40 W/ 4 pi (2.2)^2

=0.657 W/m^2

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