## Electric field amplitude of a sphereical wave

1. The problem statement, all variables and given/known data

What is the electric field amplitude at a distance of 0.67 m from a 90 W lightbulb? Assume all the power of the bulb goes into light of a single color with lambda = 500 nm and assume the bulb produces a spherical wave.

2. Relevant equations
I dont know what equations to use our prof essentially skipped this chapter

3. The attempt at a solution

I dont know where to start this problem because I dont understand what relationships to use

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 Recognitions: Gold Member Homework Help Hello sklotz. Welcome to Physics Forums. When the prof skips the chapter, we just have to buckle up and dig it out for ourselves. So be resourceful, grab your text and browse through that chapter. You should be able to find a formula relating intensity of a spherical wave to the power of the source and the distance from the source. You should also be able to find a second formula relating intensity to electric field amplitude.